Racing and aerobatics are two different animals. The Zenoah motors are designed for high rpm - take a look at their published power/rpm curves. Most aerobatic motors are designed to be propped around 6500 rpm (for 70-100cc motors). Zenoahs develop their best power + 9,000 rpm. If you want to use a Zenoah for aerobatics - use a smaller prop and let it wind up.