Pretty much gets adjusted again every time. I build them so the battery pack can get shifted quite a ways back. I too love the flat spin and stunts that start inverted. Tail heavy I don't do exactly but I do CG at neutral then move the CG as requires a little at a time until I get it where I want it. I always have students start with the CG just a bit on the nose heavy side though then move it as they get used to flying the plane.