Picked up some 6mm MDF from Bunnings over the weekend and cut it by hand tonight. It's pretty easy to work with, although drilling holes will probably be a bit of a PITA. I'm using nopheads simplified frog design, and since I plan to replace all the electronics with my own I'll probably wait until they're done before drilling holes for them. Pololu drivers are in short supply at the moment so my electronics are on hold until the new batch arrive in December...or until I figure out a way to replace them.