On the prop selection topic, I'll respectfully say that I think some have overcomplicated the issue. You prop for one thing only- in flight performance. It doesn't matter what your RPM on the ground is or if you are using the biggest or highest pitch prop your engine can turn. It only really matters how your plane flies.

Case in point- I've been doing the trimming on my Intruder for senior pattern flying. Lots of guys run an 11x7 Scimitar prop with that plane on an OS .65 with a Jett muffler. Their planes come out around 7.5 pounds and fly nicely. I went with a heavier engine (Novorossi .60F) and wound up just a tad over 8 pounds. The engine could turn that 11x7 very well, and you could hear that it was in its happy place RPM wise. But the plane didn't fly right- hot straight line speed and not enough vertical. 11x6 was worse. So I tried a 12x6 APC and got what I was looking for. With each prop, I played around with engine tuning to be sure I was peaked at the in flight RPM. A 12x6 Scimitar gave me a little more straight line speed at the cost of vertical performance. On a different plane, that might be great. But for pattern, it wasn't.

So with the prop I've settled on, I'm turning about 2k less RPM on the ground than with the 11x6. The engine probably isn't making its peak horsepower. But the plane flies right. I could probably experiment a bit more and find that one brand of 12x5 was better, or maybe not. But the plane is performing well, and I'd rather spend my time fine tuning it and myself for competition.