It is easy to scratch build a .40 sized trainer to come in at less than 5 pounds and take ANYTHING a sport .40 engine can dish out. G-forces [stress loads] are a multiple of weight and speed, so every extra ounce of dead weight will easily become half a pound of [avoidable] stress during a full speed pull out. The art of model design is to get 5 pounds worth of stuff to do 10 pounds worth of work and I think most of the run of the mill ARF junk falls well short of that mark.
A rule of thumb for scratch builders goes like this, if you don't fold one every now and then, you're building too heavy.
