Yeah, that's why he asked about A FORMULA. Not like he might want to learn something, being a new designer and all. Yet I didn't get all technical and give him one, even though I have it right here. I suggested putting the wingtips near the vertical CG and I gave him two references - put the wingtips about as high as;

A) Middle of the fuse
or
B) The thrust line.

Also, check the pic I've attached. It's a front view of a P-51 with a line from tip to tip that shows the relation to the thrust line. If you want aerobatic, this is how. If you want tamer, add more dihedral.

If he really wanted to find the vertical CG, it would be easy enough. Mark the fuse with a vertical line at the horizontal (normal) cg location. Then let the plane hang vertical from the prop crankshaft. I line straight down from the crank - like a plumb bob - will cross the vertical CG line at the vertical location of the CG (horizontal too).

Seems that some guys get into RC partially to talk out their behinds instead of actually learning something. And then start with the sniping when someone suggests a better way. Hey Crankypants, I think you should swap usernames with this guy.