The forward deck on my boat is cored with plywood. The fish box is insulated with foam around it. As for the non-skid there are several ways to go about it. If you can save the skin off the liner and it is in good shape (mine has spider cracks in it) then you can just re-use it. I think most here have just applied a commercially available non-skid to the top of the new floor over the gel coat or paint depending on which you use. You can buy a non skid pattern from a company (sorry dont have the link to it) or you can pull a mold off your existing non skid and make it look factory which will be a lot of work. here is what GW204 did
http://www.classicmako.com/forum/top...TOPIC_ID=11920
strick