I just found this forum and have a question. I have owned several plastic sit on top kayaks and used them for fishing the Galveston bay system for years. I would like to make my own but am not sure the idea I have would work. Cut a piece of 1/4" plywood for the floor, use foam to build the sides up about 6" and put about a 4" piece of foam on the bottom. After shaping I would fiberglass it. About how much would one square foot of fiberglass weigh if applied heavy enough make the boat rigid?