Here's a question that's probly been asked before in many forms. I'd like a bit of input from some of you more experienced (Ok thats all of you) Let's say a plan calls for six mm, or 1/4" ply with taped seams and epoxy. Would there be an equivalent in strength say with using 4mm ply and glassing/epoxying both sides? Ok probly a bit more flex,but that might well be overcome by a bit of extra bracing. Moving on, is there a formula, or guesstimate of what is substitutible? I know some of you guys use 3mm where thicker is called for, but I have in mind The 15' Dk dinghy. The individual panels are not that wide. This is a stand uppable inabble boat. It calls for 6mm and 9mm ply. Would there be any benefit with weight/strength either way?