[oldfielder]

I haven't followed your research, but I'm wondering if pitch would have had a more dramatic impact in the direction you were trying to go. I think you need a certain diameter to push water, but the proper pitch is what is really going to dictate your forward motion.
Did you center your research around WOT with the old prop? It will be interesting to see if you achieve you Engine's spec. with this prop-I think it is 4600-5000 for the MPI.
Two big guys and a full tank is a lot of weight-it may change quite a bit with a lighter load.
Good luck.
I'm in the middle of a possible prop. switch and I feel your pain because I'm nervous about pulling the trigger and not getting the results I want.