Pool noodles work the best, you can cut them, nylon tie them. the spray stuff, will blow apart your hull if not carefull. and they do after time absorb water.
even ziplock bags filled with packing peanuts work.
but pool noodles work the best, and they have great floation.
Pipe insulation also works
line the outside of the stringers with them, your good to dunk it.
NT