While I agree with heavy reinforcements of any plane, I do disagree with minor things that make sense on lightweight ARF trainers. I've seen 4 or 5 at the club and they all need the same things to survive routine beginner bashings. If you don't have nylon bolts for the main gear you could run into trouble ripping out the fuselage bottom. Triangular stock on the firewall corners doesn't add significant weight, nor does a little somewhere in the middle at potential breaking points. It is just a little insurance. I'm surprised at the corners being cut on the trainers that I've seen so far.