I have the same vessel model and year.I took my seats out last year.
The bench seat was purely fixed by 6 large dops of sealant
. I lifted the front edge and carefully used a sharp steel paint
scraper to cut the sealant
blobs in half, then the bench seat lifted up. There was no indication there had ever been any screws, as the fibreglass mold
is seamless (watertight) in that area.
Once you remove that, the back came away by the same method.
I have replaced the same way over six months ago and all is sweet.