Is it alright to use 2#pour in foam in a 16 foot aluminum lund boat? Will it be dense enough or will it absorb too much water over time? I am leaving a path down the middle for any water to drain to the bilge should it get in the hull.
You could put some plastic film down first then pour the foam into that, it will still take whatever shape it has to and give you your flotation but you have the plastic barrier to help keep the foam from absorbing water.
Just be sure to seal the top too so it doesn't get water from there.