I'm in the non-049 camp as well - my easiest-flying model is my biggest, a .35-powered Ares. Not an ideal trainer, though, for obvious reasons! While a 25-35 size model will tend to pull harder, I wouldn't discount it provided it's on decently long lines. The lap time is still likely to be nice and sedate, and you have plenty of room to manoeuvre and make mistakes. Not much good for little kids, though, as the line tension would definitely be too much.

When it came to finding something for my 7-year-old to try recently, I ended up making a sturdy little profile model for a muffled Enya 09. This turned out to be just right for him in terms of stability, speed and line tension. He managed about half-a-dozen laps on his own at his very first attempt, before ending up in an unrecoverable dive (which caused no damage at all).

That said, I think Jim's suggestion of a Lightning Streak Trainer is a very good one.

Steve