I have an ST-G75 mounted sideways in a SIG 4*60, fitted with a Bisson Custom Mufflers Pitts-style muffler. It definitely needed a long run-in and the first several runs had to be sloppy-rich but once it got broken in on the test stand it has been a great engine. Easy to start, lots of power. I was using a 13 x 6 APC prop on it last season, but I may switch back to a 12x7 or 12x8 this season.