As per R9, you cannot have a sheet of plastic starting larger than 12"x24", so would this be illegal? I would search on the forum for discussion but the freshmen are a bit too excited to stick their cutting tools into it.
It doesn’t matter what size sheet you start with, as long as all the parts you use on the robot can be arranged to fit into 12x24” then you’re good.
VEXPro parts are not part of the EDR line, so they are not normally legal. In this case, however, you can use polycarbonate purchased from any source as long as it meets the requirements in <R9>.