"Capt. Geoffrey Thorpe" The Sea Hawk @See My Sig.com wrote:
You are correct the center of gravity will align with the aerodymanic
center of effort. But, where are the Cp and Cg on the "jet pack" with
ducted fans in the "tractor position" - and how much stability will it
add in a hover?

Obviously the Cp and Cg are close enough together that it doesn't matter
much where they are - it appears it would be unstable with or without
power.

In fact I should confess that I only posted my comments in a very modest
effort to promote lighter-than-air (LTA) as a more viable option for such
things. Of course the "open" technical challenges and usage tradeoffs of a
personal "portable(!?)" airship are quite different from rotorcraft.