There is no such thing as a 'perfect' prop. EVERY prop, no matter the design, pitch, or size, is a compromise. I ran a vented prop on a previous deck boat. Basically a big heavy barge with a 4.3l on it, but once it was up on a plane, it was nearly a flat bottom hull. In other words, it suited a vented prop really well. The vents helped kick the engine rpm up to get the tub moving, and once at cruise, it was past venting and the nearly flat bottom hull let a higher pitch prop get up to speed. Beyond initial takeoff, i didn't ever notice it was a vented prop, nor did it change my cruising RPM or efficiency. Like you mentioned, it is all about proper propping for the boat. It sounds like you didn't find a good vented prop for your test scenarios. I've had plenty of non-vented props that were horrible on boats, its all about matching and testing.
