Great news. the carb mods are great on the very top end. I used a 9X6 prop with 5% nitro Omega. And Got 17,000 . My GP 42 is showing it's age, it was not well cared for when I got it. But I got it cheap enough. the compression is getting a little weak when it gets hot. But I called ACE and finally got that head gasket ordered and installed, so we are not so over compressed now.