there are many different types of nida core I am thinking of using a nidacore with fiberglass on both sides from manufacture,but I don't think polycarb panal would be useible, what i am planing to do is to bond the panals ( plywood or nida core) to the stringers with a bonding putty (polybond) then to glass around the flange I left when i cut my deck out. My boat being an inboard I can also glass along the inside of both stringers, I am also going to install rod lockers outboard of the console as i saw in sombodys rebuild on this site, this will also inable some glass tabbing on the bottom of the flange where i can reach I think this will be plenty.I am going to do without foam fill.