If you have seats that go all the way across then suspend your floor from those seats. When I have added floors to small tinney skiffs, I created a 90 degree angle from aluminum and attached it to the seat side letting it hang down to where I wanted the floor. Then used 5/8" 5 ply plywood for the floor. Worked great, no uneven surfaces to deal with. Also cut a hole and added hatch doors to get under the floor for storage, especially my anchor in that front section with the V.....just some food for thought !