Don,

Yeah, the OS FX has just proven to be the best all around 2548 engine. A lot of other engines look good on paper, but don't seem to have the power to back it up, especially with the large props and stock mufflers required in 2548. Some engines even do well on a small prop but really die with the 10" props. Now that the Magnum .28 is legal, it's not a bad option if you can't find an FX, though the carb has a lot of issues, so keeping it running reliably takes some doing.