I take my duties as Forum Resident Dummy quite seriously, so here goes.  I've been reading about vertical CG, but I'm not sure what is meant by that term.  I've learned from my mentor that if the plane is hung by the leadouts, and the fuselage hangs level, or maybe just a hair nose-down, the leadouts are in a good position to start from.  Is that vertical CG?  Glen

I've learned from my mentor that if the plane is hung by the lead outs, and the fuselage hangs level, or maybe just a hair nose-down, the lead outs are in a good position to start from.  Is that vertical CG?  Glen

What you are doing there is finding line rake. Even on line rake it just a guess. You have to fly it to determine the correct angle for that plane and conditions. Everything I know is by trial and error. I have a good idea what works and what doesn't after building hundreds of planes. I have no formal training in engineering or Aerodynamics. But what I have found out is if a plane is Straight and "light" with less concentrated weight. it is easer to trim with less weight.

Lots of good info here, but I don't think your question has been answered Glen. The CG is situated at one exact point in the airplane. In addition to fore and aft position, it could also be high or low in the fus. Wherever it is, it will hang immediately below the leadouts. So if it is high in the fus it will make the plane hang outboard wing-low. If it is low in the fus it will hang wing-high.  This is vertical CG.

A lot of well meaning, and good advice, but I suspect that your question, though answered, might need a little more clarification.

The method you describe, will indeed help you set the leadout fore and aft location, to a safe and good, approximately correct location.

All that is now needed to find the same kind of location for the vertical CG, is to look at the plane from the front, or back, while hanging on the leadouts.

The wing should hang straight up and down, perpendicular to the ground, when the vertical CG is close to correct. If you're looking from the front of the plane, and the wing is tilted to the right, ( towards the bottom of the plane) your leadouts are below the vertical CG. Of course tilted to the left, and your leadouts are above the vertical CG.

You can imagine some of the trim problems you could have when there's a lot of mismatch with the Vertical CG.

Bob Gialdini once explained a simple way to get pretty close when you design a model. He stated that there's a lot of math that can be used to determine the exact location of the CG, both vertical, and fore and aft. He also told me that for most of us, it's just too much to figure. Hwe then told me what he always did. He drew a scale outline of his design from the front onto stiff posterboard. He said to include everything, gear, stabs, wing, fuse. Cut it out as accurately as you can, and find the spot where it balances on a pin point. He said that this point will be as close as we need to be most of the time

Nowadays, I use the CAD system. I draw out a scale outline of both the front and side view, then have the computer find the center of mass. Close enough.

Please see also posts in the ARF section regarding Brodak P-40 and Score ARF
Have a merry christmas