Has anyone used a spray in foam for buoyancy? in the hull of their boats.I think some of that spray in stuff expands to much. I was wondering if anyone used anything and what was the results.

I have used it before I put the deck on so I can trim it. dont use it in an area that it cant expand

I have used it in my bow of my two USS Missouri's and some at the stern.

Use with caution. If its in an enclosed space on a hot day it has been known to come back to life, and the force of expansion can be greater than the deck to hull join strength.
It is less buoyant than air, so allowance has to be made for its weight.