ORIGINAL: Ram360
Your at 63 with a 22x10, that 4 blade is turning at 6000. Not much of a difference. I just think it should of pulled harder.
You also have to overcome the drag forces of the extra blades. I don't have telemetry on mine, but I would expect that the 22x10 prop is unloading in the air closer to the numbers Tony is suggesting, which helps boost performance.
I also don't tune for max rpm's on the ground, I've learned that the hard way.
With the 4 blade did you notice a significant increase in rpm's in the air when you where coming down for a low pass?