I have had Really good luck just using the pink or blue foam alone, or with a couple coats of latex paint over for protection you do have to be a little careful on grass - asphalt and cement are out. Water is GOOD ! !
My Initial though was to fine tune the hull then glass it. But it is so durable It will easily last 50-100 runs - unless you hit a dock or something solid. 2" foam has enough floatation to be able to sand 1/8 - 1/4" off and re -shape or smooth off the bottom a couple of times.