How thick should my powerboat hull be?

Hey all. I have a 12' boat that i am redoing. I have the deck separated from the hull and i am replacing all of the old rotten wood with either nidacore or coosa....havent decided yet. Anyway on the bottom of the boat there was a 1/4" sheet of plywood cut and layed down flat on the bottom of the hull for additional support. My plans are to replace this with a standard stringer setup and I was going to reinforce the hull since it is only around 1/8" to 3/16" thick. What materials and how much could I use to try and keep the weight down to a minimum but still add enough strength to hit a few waves. It will have stringers placed about 12 - 15" apart. How many layers...what ounce....what kind. Would be using epoxy. thanks

 

buy and read 'the elements of boat strength'