: 3/4 inch AC plywood makes really good forms
3/4 plywood is pretty expensive.

Actually, most cabinet shops throw away pieces of 3/4" plywood that are smaller than 16" x 24" as it is not of use to them in any cabinet use. They usually toss it in a bin or dumpster as waste. You could go to some and see if they have anything like that and just snag it and build your forms ( free ). My Great Auk forms will be made of some of the best Oak 3/4" plywood you've seen. Just watch out for the newer stuff that has the particle-board core. Hope that helps!

Rehd