RE: Variable CofG
I have found that not everyone thinks lighter flies better.
Weight is definitely the enemy when doing 3d stuff, but for anything else a plane can be too light. Especially for IMAC or other precision aerobatics, some added weight makes the plane steadier and it presents better.
Also a lot of people prefer a little extra weight if it is used to make the plane stronger. It's very irritating to put all that money and effort into a new plane just to knock the gear off on the first landing and tear up the bottom of the plane.
TF