I bought a new Sea Nymph GLS19 in 1992. Still have it today and fish Lake Champlain & Lake Ontario. The factory aluminum floor is the way to go. I helped my buddy many years ago replace his plywood floor in his Starcraft. What a pain!!! Glad I don't have to worry about that.
I'm hoping to upgrade to something a little bigger in a couple of years. I want to stay with an aluminum boat with a Aluminum floor if possible. Good luck with your search.