Applewood, Sorry for the late reply. You need to define the body position at the centre of mass, and never let them deviate. Mind you, you can still distribute collision geometry around this centre as you wish, or redistribute mass. E.g. in a sphere shape, box shape, ring shape, whatever. But the logical position of an object should be the centre of mass for the body. E.g. a trick to keep a car from rolling over: define the centre of mass (car pos) at the bottom, or even below its chassis. The collision geometry will all be above this point, but that is fine.