[sdcantrell56]

You could also do the mentioned 1/4" thick plywood or even go down to 1/8" thick and then laminate it with some fiberglass cloth and epoxy, which would make a very strong, stiff, and light board plus it would be very cheap and give you the opportunity to work with composites. Be sure to use a good plywood though like baltic birch or even better, 1088 meranti or okoume plywood.