Tarot 650 quadcopter - quick overview

Hi All!
I built Tarot 650 quadcopter. It's nice frame but still not as good as it can be. Even for it's price engineers had to spend some time flying it.
Weak points:

1. There is not too much space to put electronics.
2. Folding joints are bad, after some time bolts starting to fall off. I lost two from arms during flight and one form leg.
3. Legs are fragile, especially 10mm horizontal piece. I broke them very in first landing when started to tune flight controller.

Let's go over all these weak points and try to enhance them:
Fragile landing skid
Joints and Landing gear