Buster

We sort of skipped your question on the CG. Moving the motor position will not change the book proper CG location. That will not change but your actual CG likely would change. It is key to get in the range shown in the book (measured properly no eyeball stuff) and then fly the thing.

Trim flat into the wind at cruising speed and then roll inverted and see how much down it takes to fly flat. A little down is taken by most IMAC folks to be just right. Lots of down and you are nose heavy while having the plane climb with no down in it would be tail heavy. That must be done right after thrust checks and before anything else is checked or changed. This will make a difference to everything else you are doing with the plane.

Give it a try then let us know about the knife edge performance you see.