rodmaker~
"Blue i use a skill saw bot i clamp a straight edge to the plywood and use that as a guide cuts very straight that way."i was going to jump in earlier blue on this and yes what rodmaker said. we have a contractor grade skil saw, purchase a good plywood blade, and use a clamp on straight edge guide from rockler woodworking (they come in different lengths, we have 3 or 4 of them) easy to unclamp, slide, adjust and saw. we have cut all sorts of sheets of plywood thickness's (length and width) and also birch, oak and maple......have to say a perfect clean cut every time.
ps, the guides hang nicely on the garage wall and come in handy quite frequently for other tasks.......