"Supposedly" (I say that because I really don't know) it will make it harder to get on plane, but it won't affect the top end. "Supposedly" the tip of the blade provides the top end speed and that the entire blade affects planing. I know that from my experience, that I'm needing more pitch, but that I'm experincing greater slippage with the higher pitch props. I'm about to regear so that I can get below 30". I'm sure that you are already using some really low gearing, but I'm wondering if you can go even lower.
I tried a Spinelli cleaver this past weekend and was really impressed by it. Water conditions wouldn't let me make any wide open runs, but the prop felt really, really good. There might be something in that for you too.