Made hole in rear seat bottom through upper skin. Cored in and around hole. Filled hole with micro. Shaped micro into taper. Tank bottom and aluminum fuel boss will go in this hole.
Layed up 24" x 48" carbon sandwich with 1/4" foam core and 2 bid 90 degree carbon each side. Peel plied both sides. This will be stock material for upper copilot footwell tank.