Call Josh over at Steve's Custom Props in Quitman. He'll shoot you straight. He helped me setup my rig and predicted the result of every change we made.
As you might already know, weight distribution makes a big difference as well. My XP1860 porpoised horribly until I moved the two TM batteries under the center console, it helped a lot but still porpoised. Jackplate, then a new prop, and she's doing about all I could expect her to now.
Yours have a jackplate on it? If not, I'd consider that before a prop.
If you're not living on the edge, you're taking up too much space!