T: I gues it is really Polyurethane Mix and Pour Foam.
I googled High Expansion Foam, and after wading through the fire fighting foam, I found:...
Foam I always use high expansion liquid foam. Stand the boat on end and pour it in and it will immediately react and turn into waterproof foam...
Pitch way low I run a 13" x 17" on a similar boat but only have 250hp. You are way low in pitch. I am moving to 19" for an easy cruise of 40...