I've got a new Toyota Highlander with roof rack.  I'm not too sure about putting a couple sheets of plywood on it.  I've been looking a Yakima for something I can add to make carrying wood, Plywood and other lumber. safer/easier  Anybody using a Yakima rack for carrying wood who would like to point me in the right direction.

Try Rhino rack, their platform system is darn good
https://www.rhinorack.com/en-us/

When I had a Mazda3 with a Thule rack or a Pilot with the regular manufacturer rack, at least 3/4" sheets were rigid enough that I could just put a couple on top of the cross bars, and then use one ratchet strap in front and one in back, looped around each side of the cross bar and it was pretty solid.

I've carried plywood this way more than once, usually on stock SUV roof racks. Be aware that there is a massive amount of force (lift) if you are running along at highway speeds, trying to rip the material off. Use quality ratchet straps or 1/2" rope and know your truckers knot.

And never follow someone else hauling this way...

RMW

  You mean I can't just hold it on with my hand out the window and a buddy doing the same on the passenger side?   

       I actually saw this happen at a HD years ago. They got as far as making the turn from the parking lot row onto the main parking lot drive. I think they managed to hit maybe 10mph. At least they lost it in the parking lot. 
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   Almost got two sheets of drywall on my windshield one time. Truck with cap in front of me at a traffic light. Must have just left a worksite. I noticed the sheets seemed to be moving around a bit while stopped at the light. I don't think it was tied down at all. They probably forgot but ........................... Truck hits the gas when the light turned green, I didn't. Drywall cartwheeled into the air and smashed on the pavement right in front of my car.

Seth

Go slow. 30MPH (tops) slow. Strap as if your child was sitting on it. Stop gradually.

One sheet is about 100 pounds. Most roofs can handle 100-200 pounds. So about 2 sheets is max. That is not much.

All things considered, it is MUCH, MUCH better to just get or rent a trailer. Or cut to size at the yard so it fits in the trunk.

If I'm hauling sheet goods, regardless of weight, they go inside my '15 Expedition EL with the back door solidly closed, and ratchet-strapped to the underpinnings of the second row seats that have been folded down.  Lumber up to 10' can go inside in low quantities.  Longer materials (trim, lumber up to 16', plumbing, conduit) all go on the Yakima JetStream bars on top of the Expedition.  That said, all will be shrink-wrapped at the front end with a short length of duct tape securing the shrink wrap to avoid wind separation and destruction of the materials, especially trim.  I watched some bozo totally destroy a load of shoe molding because he didn't tie the front ends together to resist the wind.  I also watched another clown spread a load of sheetrock on the highway because he apparently didn't strap it down inside a shorter-length Expedition, and didn't tie down the back door. 

Two things watch for when transporting sheet goods on the roof top are:

1.  Air lift.  Air gets under the front of the plywood and the lifting pressure can be immense.

2.  Hard stop inertia.  A hard stop will toss the sheet goods forward will gusto.  A sheet of plywood 3/4” x 4’ x 8’ weighs about 60 pounds; pressure treated, about 90 pounds.  A hard stop and the sheet can fly off and decapitate someone.

Two things watch for when transporting sheet goods on the roof top are:

1.  Air lift.  Air gets under the front of the plywood and the lifting pressure can be immense.

2.  Hard stop inertia.  A hard stop will toss the sheet goods forward will gusto.  A sheet of plywood 3/4” x 4’ x 8’ weighs about 60 pounds; pressure treated, about 90 pounds.  A hard stop and the sheet can fly off and decapitate someone.

Good Point.  Does anybody make a roof rack with an air deflector on the front - that would eliminate  "air lift hazard"

I think you can make a clamp-on piece of hardboard to eliminate the gap under the plywood and thus eliminate the uplift hazard.  I never tried to do so, but it seems doable. 

Most of my roof-rack plywood hauling was done on fairing equipped racks. The fairing reduces the wind noise quite a lot whether you're hauling something or not, so, I find it a worthwhile addition.
That said, my current cars use the newer "aero" cross bar racks, and don't use the fairings.

I've not had a problem with uplift, glass sunroofs are great to help monitor the load while in transit 

Stow in place cross bars. That's a cool feature.

Seth

My Chrysler Pacifica comes with a convertible roof rack that be moved into place when required.  I have had no reason to use it and I don't know how to make the switch.

Subaru has had a similar system for over a decade, but it, too, is weight-limited. 

I am a member of the Chrysler Pacifica Website.  And other than the fact that the speedometer will spontaneously shift from mph to kph, mine has been flawless.  (Switching back is easy.)

Others have not been as lucky.  But I will say that many of the features (like the stow n' go rear seats) are well-thought-out.  The ride and handling are exceptional for a mini-van and quite comparable to a well-sorted out sedan.  It is also quiet at cruising speeds, offers good acceleration, and has seats that are comfortable for long trips. 

I have yet to need new brake linings even though I just clocked 102,000 miles.  (I don't understand it either.)

But others have had engine problems and transmission problems.  Enough have complained that is clearly is not an isolated incident.

When people ask me about it I say, "It's the best car I have had in recent years, but I cannot recommend it because of all the reported issues."

Two things watch for when transporting sheet goods on the roof top are:

1.  Air lift.  Air gets under the front of the plywood and the lifting pressure can be immense.

2.  Hard stop inertia.  A hard stop will toss the sheet goods forward will gusto.  A sheet of plywood 3/4” x 4’ x 8’ weighs about 60 pounds; pressure treated, about 90 pounds.  A hard stop and the sheet can fly off and decapitate someone.

Don't forget to calculate the effects of INDUCED DRAG as your speed increeases and the possible adverse effects of Parasitic drag 

I got Rhino Racks for my Pilot.  They have nice, long crossbars that work well for sheet goods.  In addition to strapping down, I also made sure to strap to prevent the sheets from sliding forward and backward.  I always took surface streets home, being careful not to go too fast.  Also, never more than 2 sheets of 3/4".  I would also just slide them in the back compartment. 
Or try what this guy did when I sold him my steel cabinet...

I own a Chrysler Pacifica with the stow in place roof rack.  Never used it.

When I fold down the Stow n Go seats I can slide a full sheet of 4’ x 8’ plywood in the interior and close the door. 

I then drive home and back onto the driveway.  I setup my saw horse cutting setup behind the car.  I place a roller stand behind the van just a little higher than the saw horses.  I then slide out the sheet over the roller stand and roll it onto the cutting station.

I make my cuts and carry the smaller pieces into the shop. 

The Stow n Go is the only reason I got the van and the only reason I kept it after getting a Chrysler 300 sedan.

The Pacifica is surprisingly luxurious, quiet and has good ride characteristics.

I had purchased a 2019 Honda CRV with all the bells and whistles.  I kept it for 6,000 miles and about 3 - 4 months before trading it in on the Pacifica.  The Pacifica is a vastly nicer car (and far more expensive). 

I can only recommend the Honda CRV or the Civic (which shares the same engine) if you live in the south. In cold weather the engine will only reach operating temperature at highway speeds.  If you let it idle, the temperature will drop to “cold” in the winter.  So your defroster will not defrost.  It will not clear the snow from accumulating because in the snow you are not driving at highway speeds.  Honda knew about the problem.  At one point the Canadian equivalent of the DOT threatened to have a mandatory recall. 

A couple of weeks after I took delivery of my car they had a “quite recall”, that is they had dealers retrofit new fuel injectors to all the cars that were on their lot but were unsold.  It was a partial fix. 

I found out about it but Honda would not replace the injectors on my car because “Honda does not believe there is a defect”. 

I have permanently divorced myself from Honda and all Honda products. 

Quite aside from that, the SUV (Sport Utility Vehicle) was not sporty, lacked utility, and was barely suitable as a vehicle.  I could not carry even a 60” long plank of wood in the cargo area with the seats folded down. 

The Pacifica is far nicer to ride in, quieter and smoother riding.  It has more utility, but no more sportiness. 

I traded in the nearly new Honda and an older Sonata plus $800.00 that I put on my Amex and I drove off with the van.  Never regretted it.

Anyone who favors SUVs over a Pacifica or the new Kia, simply has not driven both.  Image aside, the vans are far nicer vehicles.  The Honda van is supposed to be nice too, but you know how I feel about Hondas. 

Both the Pacifica and the Toyota are available with 4-wheel drive.  But only the Pacifica has the Stow n Go.  But the super delux version with captains chairs does not have stow and go, and the hybrid also does not. 

If you are looking to buy a Pacifica (or the newest version of the Dodge) make sure that you know that it features the stow and go.  Some models do not.