I get 7500 from my MVVS 35 with a Zinger 20-8 Pro, the muffler is the inverted rectangle box, with this muffler the 3W 20-10 was just to much prop, I got a max RPM of 5900, I tuned it at 5700 and it wouldn't pull vertical like the 20-8 would,,, I now have a 3W 20-8 I'm hoping to try in about 3 week's, I'm sure it will pull much better than the Zinger,,,

Hans Meij ,,, is the Krumscheid 1025 pipe a tuned pipe ??

Jim