Yet another thought on the GMS.47: I just replaced the .52 two stroke Magnum on one of my heavier sport planes with my GMS .47 (the Kaos that it lived in is down for repairs....) because the .47 can fly a 7.5 pound airplane just fine for sport with a 10-6 prop. While the .52 really churns  a 10-6 APC fast, over 15,000 on the deck, I need it's extra weight in the nose of another plane. How often can you feel OK about REDUCING the size of your engine?!  Another nice thing about the GMS .47 is that by being bored out, it's lighter than a comparable .40.45. or .46.  I look forward to buying another GMS, or Magnum motor in the future (if I can ever survive this "new economy", right?).