I think there is a tendency to over-estimate the amount of pitch needed to fly most of our models. The usual rule of thumb seems to be based on the angle of the flat back of the blade, but of course the blades are airfoils that "lift", or produce thrust, at negative angles of attack, when measured from the flat bottom. People often get the impression that with a low pitch prop their plane will reach too low a speed to fly, or at least fly well. But even though there are also losses from slippage and drag on the airframe, still, I have often been surprised by how fast a plane will go on very low pitch.
For example, I flew a Sig Little Extra on an 8x3 prop and it was quite fast. My Sig 4 Star 60 flies very well on a 14x4 prop. Both of these planes could be throttled down to 1/2 throttle or less and still fly. If you do the usual math, an 09 throttled down to, say, 8000 rpm in the air, should not be able to go much more than 24 mph using a 3 inch pitch. Yet it flies well, which should not be possible at such a low speed. I fly my 4 Star throttled well back, maybe around 5000 rpm in the air. Again, it should not be possible.
I don't measure these rpms in the air, so I can't be sure, but I do think people get unnecessarily scared off from low pitch props by a poor rule of thumb.
I see the same thing with RCV engines geared 2:1. They caution that you must use much higher than normal pitches because the rpm is only about 4-5000. Obviously this is true, but by how much? One guy flies his 1/4 scale Nieuport 17 on an RCV 120 using a prop with only 6 inches of pitch. He says he rarely goes above 3/4 throttle and it will fly at 1/2 throttle. This is way less pitch than RCV says is necessary.
So I think there are misconceptions about this. Jim