I knew about O.S. being good engines (although I don't think they're really powerhouses...then again I'm not looking for a powerhouse, just something that will keep up) but didn't think the Thunder Tiger was more than a sport type engine. I do have a Thunder Tiger .25 (the bushinged version) that's a few years old and although I haven't run it I didn't think jst from looks alone (I know, I know...) that it was really anything special. I'm sort of partial to my old Veco engines (the .19 and .45) for build quality (both have dual bearings and built like a tank) but they're UNBELIEVABLY heavy for their size.