Drawing something up, but effectively I want to go from the "bathtub" style to something more like this competition. Rather than the inner liner mold, I would lay the deck direct to the stringer with whatever bedding compound, and tab it to the hull sides. Cutting the existing bathtub floor out, and reutilizing the cap and strengthening where necessary. I would also likely add 2-3 knees from the deck to the cap.
http://competitionboats.net/benefits-of-three-piece-construction-in-boat-building/
http://competitionboats.net/benefits-of-three-piece-construction-in-boat-building/