MikeM wrote that he used 2" Styrofoam with is a great idea and it works
great. You don't even need a 4 x 8 sheet as if you have some strips of the
same which you can put under your sheet. Nice thing about the foam is that
you can cut into it and never both anything. The other thing I do is use a
piece of particle board 12" wide x 8 foot for a guide for my saw. The
particle board it great as it is absolutely straight and cheap.