Minis get twitchy when they're shimmed out. I think it has something to do with the reduction in slop highlighting all of the chassis other flaws. You can shim and untweak your car, but you're going to need some serious skills as a driver to make it work.
My perspective is that minis are like hammocks: they work best when they're loose enough to sink down into them, but not so loose that you can't get back out gracefully. This kind of jibes with FauxMako's thoughts.