I have plans for a Mill Creek 15 but have not yet started building. The MC 15 plans call for a 6 mm bottom and 4 mm sides and deck, but I'm thinking of using 4 mm for the bottom and sides, and 3 mm for the deck. I have built from plans an LT-17 and a Chesapeake 14. The Ches. 14 combines 4 mm for the bottom with 3 mm for the sides and deck, so I've some familiarity with the lighter materials. Other than the obvious problem that the lighter weight construction will not be as robust (don't ground it on gravel!), does anybody on the forum see a fatal or otherwise serious weakness to this idea?