As I recall, the trainer engine is a .455 cu. in. displacement which is a common size for the OS .46, Magnum .46, Tower .46, etc. The Evo .46 is closer to a .47 and has a smaller bore and longer stroke.

It is not uncommon for some Chinese engines to require nearly a gallon of fuel to break in well enough for a really good idle. OS & Thunder Tiger will take less time. Maybe Evo since there are run at the factory, but I can't say for sure. Most people have no trouble at all with them.