The lighter and smaller you make things, the more likely they are somewhere where the physics engine didn't expect them, and you end up on the moon. Stable 1/10 scale physics over jumps and bumps is a great testimony to Terence who made the physics engine in the early 2000s, and also me a bit, as you do have to enter the right numbers. I have visited many planets and solar systems unknown to mankind in my time with this engine..