https://sourceforge.net/projects/xflr5/

Who wants to download XFLR5 to test some hypotheses?

Random thoughts:

We tend to envision Center of Gravity as moving exactly along the design longitudinal axis and ignore any vertical component to the actual balance point of an aircraft. Just like larger helicopters have to calculate lateral CG position as well as longitudinal, perhaps we need to think about the actual CG in relation in three dimensions to explore whether CG affects roll rate (roll moment).

True CG location not only moves fore and aft, but up and down depending on where weight is added or moved. We've been taught that it isn't important. Imagine adding weight well above or below the longitudinal axis; let's say you installed an O2 tank or added nose weights. The CG's relation to the center of rotation would change and could affect the roll moment. How much, I can't say, but I'm trying to figure it out.

Paul A.
Jupiter, FL