Ok. I am looking at a old pontoon pedal boat on cl. The pontoons are 12' x 15"? I think! It's a Godfrey sr 1200 sea Ryder I think. There is no weight capacity plate. I'm guessing it's like 700-1000lbs... is there a way to KNOW how much flotation I'll have before I dive in? I want to carry 2-4...