At the Zachary contest this weekend, I took Dracula, the older, now backup airplane. On Saturday I was using a prop that had no drive in the warm, mostly dead air filled with thermals. Doug Moon had been advocating for two blades for a while, and I had a couple with me and decided to throw one on to try it out. The difference was amazing! Almost too much drive but great feel throughout the pattern. That prop made Dracula feel almost exactly like the Ferrari plane

After working on the prop and retrimming the airplane a bit, I noticed the airplane had developed the smallest of hunts in level flight, inverted was still tracking very well. This is something Doug mentioned he could feel switching to a 2 blade as well, but he felt the hunt in inverted flight. The only question I have is why the two blade doesn’t track as well as a 3 or 4 blade prop does? It was a very slight but noticeable change I could feel in the plane

Matt the difference between upright and inverted is some small misalignment of the levels in the flap and elevators.  If you can adjust that you can find a happy medium.  Your other difference between the props Mike covered pretty well as I would diagnose it.  When I put a four blade on an airplane I've been flying a three blade on, the airplane FLIES more nose heavy than the mere difference in prop weight would indicate.  I can only guess it's more weight added to the gyroscopic affect of the spinning prop.  When you went more tail heavy on your plane it made the hunting issue more noticeable to you.  Interestingly, when I've tried two blade props on my ships I don't get enough thrust when set at the same pitch as the three blade.  I'd have to increase the pitch quite a bit to get the same lap times.  That must be about blade area in my case.

Dave

Ah the extra diameter will slow the turn rate quite a bit.  That was true when I tried my 13" 3B vs the 12.25 3B.  I'd have to adjust my handle or add some tail weight to use the 13".  Your props could change pitch over time.  I left a handful of props in the car for a few very hot days and found them all to have flattened the pitch.  I would guess having them out in the sun all day at the field would do the same.  I'm going to try to be more mindful of that going forward.

Dave