This has been debated, but I'm of the opinion it makes no difference. CG is CG whatever the orientation. I have been balancing right side up for some 38 years now. What you need to make sure of is the location of the measurement for the CG. Is it at the wing tips, at the root (where the wings meet the fuselage), or at the center of the wing (usually close if not the same as the root). 25% back from the leading edge at the root is a safe location for most planes. This usually gives a slightly nose heavy balance which is good for trial flights because planes are more stable balanced this way. Hope this helps.