i would say 43 mph with that setup is good.

I agree 43 is a good number for that set up. But at 4300 rpm she isnt at full potential. I would go with a 17p and try to get it closer to the 4800 goal. I imagine a 17 will yield 4500-4600rpm. However I don't know of a 17p 4 blade that is built like a bravo or revo.

Would going to a 17 pitch prop and spinning it faster really do anything? Like I said, it gets on plane great and cruises fine. If I get the same results but spin it faster do I really gain anything?

I think the 17p mirage is going to work best for you with the torque limitations and weight you are dealing with. The 330 BB boats had a 19 mirage. See if you can pick up a used 17 and give it a whirl.