Mike I use blue or pink foam for places that I can get to like the seat or floor. When i build , I use block in the bow befor I put the decks on then add 2 part foam to fill the voids. On Evil Sandy, because it was a retro fit, I picked up the boat by the stern to get the bow down. (The boat was vertical instead of horizontal) Then I just poured 2 part foam into the bow. If you have never used the 2 part foam befor, it comes in to cans just like epoxy. You mix equal parts and pour into the chamber. 2gal. kit makes 8 cuft. I belive it also comes in a 2 quart kit. It will not melt with contact with gasoline. Blue block will if it is not coved with epoxy. Coast Guard standard states that any floatation material that is within 4 inches of the blige has to be fuel proof. Hope this is not too much info. If you have any questions or if I can help mor4e just give me a shout.