When I think about it, if someone didn't want to use a Fox engine, then the K&B .45 Sportster is worth a look. It doesn't use ball bearings on the crankshaft, but it is a strong runner, and likes to turn larger props than many two stroke engines do, more like a 4 stroke engine. So it would work well with big low pitch props. it also uses a 1/4x28 prop shaft stub so if you crash and bend the end, you can unscrew it and replace it. Plus it is still made in the USA too.  I haven't tried one but the MECOA .46 Aero looks pretty promising too.  http://www.mecoa.com/