Hi Nathan, and welcome to OldTools!
Just a couple of tips from a long-time wooden-boat owner:
1. Never use stainless steel fasteners below the waterline. I don't understand
the metallurgy, but they can fail in oxygen-deprived environments. Bronze is the
preferred marine fastener. My wooden boat is fastened with bronze, and it is 51
years old now and going strong. For a boat that doesn't stay in the water,
stainless might be okay, but next time....
2. Nothing wrong with making your own, but quality marine plywood is available.
Look for Okoume or Sapele plywood made to European standards. You might try
Boulter Plywood in Somerville, MA. I haven't seen any good Douglas Fir marine
plywood lately, and I used to work in a plant that made the stuff!
Cheers,Chuck Taylornorth of Seattle