Too bad we don't have "scratch and sniff" web attachments, because it would be nice to know what it smells like. Fiberglass smell is certainly memorable (and not all that pleasant).
I have been on boats that were 15 years+ old and did still smell like fiberglass, although most of them have had the smell "wear" off by then. I believe the smell can be stronger depending what ratio of resin to catalyst was used (if the ratio is "off" then all the components don't blend and cure as properly).
Smell is just about the first thing I register when I look at a trailer, probably because I don't like odors. I have only been in a few Trilliums, but none of them have had a particularly fiberglassy smell. So here are the possibilities that are coming to mind:
1) The smell is not fiberglass but something else.
2) The smell is fiberglass and you just got a very, very rare trailer that still smells from the factory glass work.
3) Someone has patched or repaired the trailer using either polyester or vinylester resin (epoxy doesn't smell like "fiberglass").
4) Kind of a subset of 3, but pretty much any polyester/vinylester fiberglass layup (even 40 years old) will give off that fiberglass smell if you sand or grind into the glass, and expose "fresh" glass.
can seal off the smell, but as it would be a real pain to paint
the whole inside of the trailer, it would be nice to pinpoint exactly what is happening before you do so (at least, that's how I feel).
Oh, and usually if there is a smell, it is coming from the "raw" side of the glass and not the gelcoat side. Can you sniff around with a fresh nose and get more clues?