Fitting a 90 2 stroke to a 60 sized trainer doesn't seem like a good idea for a beginner.

Another engine to consider might be the OS 65LA. According to one writer, it's actually more powerful than the 61FX:

http://www.modelairplanenews.com/cli...60engines1.asp

One advantage of the OS is that you get the option of a rear needle valve. Some people don't care about this, but I like the extra inch or two of distance that it puts between me and the knife at the front of the plane doing 12k.

Matthew