fiberglassis an OK material for boats. after owning a few that had a
balsa core, I'd never do that again. with age and previous owners, you
can end up with balsa/sponge core---suitable for a land fill.
I wrote to "This Old Boat" magazine to see if they ever did a story or
put together a list of solid fiberglass boats. the answer was, "no".
good research project. talked to a fellow who had just put a new
transducer in a Fischer motorsailer, he said he was amazed to drill away
and find the hull to be an inch and a half thick, solid glass. yeah!