I have a different approach. Since I'm working on increasing squat depth post hip surgery, I bought 3 different sized stability balls and a base for them. I started with the big one and squatted to that, being be careful not to bounce off the ball but merely use it as a guide and emergency support. Then I moved to the next smaller one after a few months. Now I'm on the lowest one. If I increase the weight significantly I warm up with the next higher one and then work down to the lower one. Seems to work pretty well and I think it trains the "rebound response" which the box does not.