Hi,

If you lift off the seat a little and have a hand position on the bars with no / very little
forces acting on your hands you then must be balanced with your CofG over the BB.

Moving your hands forward will will tip you forwards, and back tip you backwards.
Moving your bars up will tip you back, down tip you forward.

What I'm saying is if when you balance on the pedals if your butt stays in pretty
much the same position, it indicates for your normal riding position your CofG
must be pretty much over the BB, as your body shape is near identical.

If when you balance on the pedals with your normal hand position your butt
moves forward or backwards just above the seat, it indicates for your normal
position your CofG is not above the BB.

My folder has a fixed (too short) effective toptube and stem length. Only
barheight is adjustable, and the geometry doesn't fit any fitting system.
The seat is as far back as it will go and set to the right height. The only
adjustment left is the bar height. It is now much easier on the hands.

rgds, sreten.

To add : balanced over the pedals with your butt hovering over the seat
the CogG is over the bottom bracket. The load of your body weight is
shared by the wheels in proportion to the horizontal distances to the BB.

As long as your body shape remains the same, so does the wheel loads.
Sitting on the saddle doesn't change the wheel loads, it changes the
distribution of the forces at the 3 contact points, and causes some load
on the hands for the whole body position to remain balanced out overall.

Dynamically the forces on the seat, pedals and bars are oscillating, but
the CofG and static vertical loading on the wheels remain near constant.