I know this is an older thread, just thought I'd bring it back forward since I found some info in it that I felt was relevant to a boat I'm working on, that being a 1978 Miss Madison.
After rereading Lohring's post, I decided to follow his lead on the right sponson transom. So far, I've redrawn my set of plans, basing the reworking on measurements taken from the full sized Pak hull, to get the boat more accurate. To get scale thick air traps, I've gone with 5/32" ply for the sponson insides and engine bay walls. Both on the full sized boat are 1" thick so using the 5/32 ply will only be .00625" too thick, before paint. My only question, at this point, is how thick do I need to go on the plywood for the right sponson transom? I'm thinking, with a 1/16 outer aluminum skin and 3/16 inside backer, both of 6061, that 3/16 ply would be heavy enough. Since the left sponson won't have the same load, I'm thinking 1/8" ply for the transom with 1/4" ply sponson sheers. Anyone have any thoughts on any of this?