So, this is a MC gas tank?
The orange is the 2 piece, clamp shell molds?
Maybe lay them up with a little extra wetted out CF on the flange, make a silicone bladder (which will stay inside the finish tank) and place in on the wet lay up, clamp the 2 mold halves together thightly, add air pressure (positive pressure molding) to the inner bladder to compress the laminate out to molds and let it fully cure.
Demold and you will have a small seam on the over lapped flanges to sand and finish before clear coating with automotive clear coat. The bladder should stay bonded to the wet resin sides but if ruptured, it SHOULD (don’t take my word on this at all…) retain the fuel inside?