Thx for the added input...
I will have to re read this a few times, then re look the Seneca PG system, as I have laid it to rest... which is a shame, as I bought so many of the Incra rails to make for a well rounded system. But it was all so unreliable, I abandoned it, and till this thread, forgot about it. Sure glad Buggsy found a solution, which maybe his video will make the problem and solution crystal clear.
A few General comments here regarding rail placement.
1) I also have the TSO square for the rail... TSO makes very precision machined products for sure. But in this case, "square" relies on the rail itself, not just the TSO component...and this also turned out to be unreliable. When I insert the TSO rail square and check with largest 26" WP square, the Blue Square is NOT square to the WP square. This is NOT a defect of the TSO product, instead, its a tiny difference at the connection between the TSO product and the rail, a few thou at most. It took some blue tape to make up that difference to get it square. When cutting an 8ft sheet using this method, the smallest out of square will magnify out of squareness at the other end. IMO, trying to make a large run, such as 8ft. square at one end is not an ideal system. for 2ft, prob. yes, as the error at the end would be 75% reduced. The Festool rails are not robust extrusions. If the rails were designed knowing of all these aftermarket products being inserted in them, I would have suspected they would have reinforced the back area of the rails. So I am very careful when using end squares. Again, this is not a knock of the TSO product, its just a warning that any end rail square represents half the equation to square, its not always plug n play, always confirm.
2) After the frustration of the Seneca PG, I developed a different placement system for my rails. As users well know, there is two types of cuts on a rail system. First the usable work piece is under the rail, typically larger pieces. (blade kerf is not relevant, as kerf is taken from waste piece) Second, the usable piece is in front of the rail, such as cutting multiple strips. (kerf is removed from the usable piece)
The simple system I developed works well, is simple, fast and with a little bit of practice produces parallelism as good as any system I have tried. I use two WP rules with WP-2 stops.
https://cdn.woodpeck.com/media/catalog/product/cache/26208d9473ddf6b783395684c4053ce8/m/a/main2_rule_stop-2_2_9.jpgIf I want 20" pieces, I set the stop at 20"+ kerf, ~1/8". Or add a 1/8" kerf block to front of rule if you dont want to remember to add kerf. I place the two rules about hip distance apart, set rail closer than 20". I then push the rail forward using the 2 rules, holding the rules flat to the work piece... when the stops hit the end of the work piece, the rail is parallel and set to the proper cut distance. No longer do I need to do the up n back rail dance as when marking one end. It's reliable, fast, and u can teach others to do it quickly. I learned, once the stops are close to touching the material, go slow, try to push them so the both touch at about the same time. maybe 5 seconds is all it takes.
There is some downsides... you need at least two rule length pairs and 2 stops. So its not cheap by any means as you can see the prices of the rules and stops. OTOH, the rules are very accurate and have many other uses. However, there is other rules on the market with stops, or you can make your own using some Starett tapes and their are many stops on the market... even incra products would work. The WP rules are pretty wide so they have decent surface contact area to the rubber cutting strip on the rail. The wider this is, the better, hence a homebrew solution would be even better.
The other downside is, Cutting 4ft pieces is cumbersome as the rail is far away, and would require the WP 49.5" rule. With tax and ship is prob. $90+ each. But they are very accurate vs. marking with a tape measure, so u can weigh the pros n cons of the longer rules. You can also make some 12" blocks to use as spacers and just use a pair of smaller rules. Simple, not error prone if your space blocks are an even foot.
