12ft Flat Bottom Setup

[abwehrly42]

I have a 1236 flat bottom with a 25hp Mercury turning a 15 pitch Powertech SRA3. I originally had the jackplate set as shown in the third picture. I was turning 6000 rpm and hit 39mph. I raised the jackplate one set of holes to the height shown in the first and pictures. I was turning 6300 rpm but still only running 39mph. The trim pin was in the fifth hole both times, which is just barely positive.

Would it help to add some cup to the prop? Or do I need to drop the jackplate back down and be satisfied with 39?