No such thing as a dumb question. Really.
Plascore can be thought of as funny looking plywood.
With plywood I used to build temporary rib like formers and then attach the side panels to the temporary ribs. As soon as you pull the front end together and rear end to the transom it looks like a boat. Straighten it up. Make a 4x16' foot panel for the bottom. Put the bottom panel on top of the upside down boat. Weight down the ends so the bottom panel touches the chine all the way around. Trace out the bottom panel with a pencil, following the joint between side panels and bottom. Take the bottom panel off. Cut to pencil line, at the appropriate angle. Actually I like to cut 1/4" wider than the pencil line.
Now glue down the bottom panel........resin, resin putty and boxes of nails. paint cans, skill saws, chain saws, what ever you have to put weight on the panel.
Once the glue is hard use a right angle grinder or belt sander to grind back the chine edge of the bottom panel, which may be a bit wide here and there because you didn't cut tight to the pencil line. Now fiberglass it. Don't worry about the exposed cells in the Plascore at the chine edge. Just glass right over it.