I have the same boat (1998) with 2 x 2005 3.3L 225hp Yamaha 4-strokes, and I can say with confidence that there is no need for increase in hp. Mine are the "older, weaker" 3.3L, as opposed to the newer 4.2L, and I have all the performance I need and more. So much torque that I can ease the throttle through getting it on a plane, and it tops out at 45-46 mph. The hole shot is amazing - you could pull 6 slalom skiers up at once without issue. No kidding. Anyway, I would not be in a hurry to increase the weight on the stern. FWIW.
// Oops - I see that I am too late with my reply. ENJOY!!