I think the Goldberg SR Falcon would be a great choice.

1. New ARF kit coming out soon
2. Very forgiving
3. Will perform well with a 45 size engine
4. Will handle up to a 61 size, depending on you skill level progression

I have used this trainer to train many r/c pilots, before there was a Buddy box. This air craft will do it all. I still have one that I built
in 1972, and it is still flying. Taught my son to fly when he was 8 years in 1991, with this same SR Falcon. Very tough.