Hi all,
I've started my build of a Joe2006. I've already learned that MDF cuts just as easily sideways as it does forward and back on my benchtop table saw (coarse carbide tips gouge easily with a single sideways flinch... my 24" skins will now need to be 23.75". Oh well.)

My biggest concern is setting up so that my torsion box is totally flat. I am trying the "bridge across the sawhorses" method I saw on the Woodworks TV show. I'm working in the front yard, full of dirt and gravel. After several hours with a level, I believe that all directions are flat. My drywall T square also indicates flat. But my eyes tell me, when looking down the side, that there is a slight arch. I'll probably sand some tongue depressors to get the correct shim.

But when a level, and a T square, indicate flat when it really isn't, what can I depend on? Is there a method that people use to get the "final word"? In a worst case scenario, when I get things put together, I can use my router to shave off any high spots, assuming no twist in the rails. Eeek!

Thanks for any pointers.