Before changing other things I would go the opposite direction with propeller pitch. Going higher in pitch may increase maximum airspeed, but not the accleration you want to get off the water. Kind of like using first gear to get away from a stoplight instead of the high gear that is used for highway cruising. Try a 10x7 or even a 10x6 APC.

On one of my Northstars I grooved a 'divot' in the fuse to allow for larger diameter props, and I believe that this is a better solution than raising the engine pod. In addition to the other considerations, increasing the height of the pod will reduce its strength. I've included a picture of modifications that I make to my Northstars (four of them) using 1" triangle stock under the pod instead of using fiberglass as is suggested in the plans. This makes the tail fin/pod much more rigid and able to handle the inevitable rough landing much better. Also note the other modifications in the second picture for improved water handling.