HKEK writes:

If the door balances at the half-way point but it takes X pounds lift
it from the closed position and Y pounds to pull it down, what are
safe/acceptable values for X and Y with the electric door opener?

That's a good question, but in practice 10 or 20 lbs is about as close as
you can get in many situations. If the mass of your door is uneven across
the panels as you describe, the force will vary at least as much as the
panel mass varies. For example, if you have an extra 20 lbs on the top
panel, it effectively disappears when the panel goes horizontal. The
standard residential door torsion spring mechanism is based on door lift
weight being proportionate to lift distance, since the door turns
proportionately horizontal. This in turn assumes the door is approximately
homogenous, not heavier in some panels than others. Violating that
assumption with a heavy panel cannot be compensated for by spring
adjustment. You have to make the other panels just as heavy, and install
heavier spring(s) for the whole works.

http://www.truetex.com/garage.htm