I'll post a few pics of some wooden plugs we've done. Alot of boat companies & Pro Tooling companies still do it this way. Building from knowledge and not trial and error. almost all wood plugs aren't even used for trial & error sessions. However a good boat builder\tooling guru can build wooden plugs that can be rigged & run to do testing. then bring it in strip the rigging & Pull Molds off of the part. I can assure you even some good cnc parts sometimes can fall short during sea trials.