I built 2 several years ago. A Piper Cub and a P51 Mustang. For me they were very hard and I did not do a very good job to be honest. That is why I never built another one although I would like to do a big scale Gee Bee but I have no doubt that would be a disaster. They didn't have the ARF style back when I built mine but that's really not the same thing anyway.