Dan Valleskey wrote:
Someone told me to
shoot expanding foam into the compartments, but I'm not too crazy about
that idea.

why? sounds like a plan to me.

Would likely end up with more flotation than what it had in the first
place.

My experience with expanding foam was sealing around a basement door: the
stuff expanded enough to bend the wooden door frame. One might want to use
caution in filling a compartment where the stuff could get wedged in and
(maybe?) crack something.