best plywood?

The answer will vary depending on your location and availability of plywood, but in the US, I would recommend cabinet grade plywood. It should have typically about 9 plies of birch. This minimizes any tendency to warp and is a strong wood. In any event, look for filled voids and maximum plies and stay away from high sap woods.

If you are looking for a good plywood, I would suggest Baltic Birch Plywood. this kind of plywood is emission free and very very strong and durable. You can read about Baltic Birch Plywood on internet and discover all the facts and advantages of this kind of plywood. Also you can visit http://www.eastcoastplywood.com and inquire about pricing, this company is a business to business supplier but they will give you a good price on small quantity.