Absolutely. I got 3 in this afternoon using the 18.1x10. I don't think I ever got above half throttle. To be fair, half throttle on my set-up opens the butterfly about 70%. In other words, half throttle is more than half power, more like 3/4. Regardless, the prop is just not enough load. Quite loud compared to glow (same prop). A good break in prop tho, for a piped set-up in a pattern plane.

Top speed in the air had to be at least 8400. It was ripping pretty good. The plane is a very light load compared to what I've been running the SAP in, both in terms of weight and in terms of drag. And BTW, today was pretty warm down here, around 90F and more muggy than we have ever run the engine in before. No problems I could tell...handled great

One good suggestion from today's gallery was to use a 3 bladed prop. I think I have a 15.75x13 3B stock. Worth a try. I need to quiet this thing down