I did a quick check quite a few years ago on a 7-5 MAirscrew with no pipe, and with a pipe on 10% fuel. Both motors were the same at 14,500 and 15,000 with or without a pipe. I obviously needed to be a bit smaller than that to get on the pipe. That is exactly what Alex was saying to me at the Nationals with his son's plane which used that motor. He was cutting the 7-5 down until they were on the pipe inthe air. His son's trainer was about 100 mph, but he mentioned a proper plane would go about 135 mph. I would guess maybe 27,000 rpm? in the air. I think the pipe is set up for about 25,000. Just to confuse things farther, My combat .15 was 18,500 rpm with the same prop which was only 500 rpm less than the Rossi I had tested. That is what it was copied from. The Uctkam needed a bit of effort to get right. I lapped the piston/cyl and changed the screws. I retapped the holes and replaced the screws. Every motor that I tried to retap had sand in the aluminum, and ruined the taps. The MDS package that came with the piped motors still said Uctkam on the case. The castings were quite an improvement from the older combat style with the opened/trimmed exh. outlet. Oh, an LA .15 went about 17,400 rpm as did my blue head ASP. My ASP has been improving a lot since then. I made new heads and fiddled a bit with it too. On a side note. The piped timing of the motor is about 190 degrees on my examples. Quite high even for piped timing. I wonder if the OP's is timed like that as run on diesel. The LA and ASP were checked with open exhaust.