I wouldn’t consider gluing insulation to the hull. Lots of reasons, agree with closed cell foam as it can’t suck up humidity and condense into water- resulting in weight and mold
and loss of insulation R factor - if that happened. I’d make snap in removable panels
if you need to stabilize insulation positions.
The first thing is to not crawl into or on the bunk without first taking a fresh water shower
if possible, if not, have a special washable blanket or covering that keeps salt
from your body, hair and clothing
from contacting the bedding. On ocean crossing
and extended cruising
we’ve learned that saltwater saturated clothing
, beddings never dry out- always are moist and thus feel damp and colder in higher latitudes, sticky in hot climes.
I’d start with new mattress and as much ventilation as I could get.