While stacking only increases the magnetic power (and output) by 20%, and doubling the poles increases the potential output by 200%.

But those are thin, and the airgap should be less than 150% of the magnet thickness per pole. So I figure they must be stacked or the stator is too thin to work with.
Who can make a usable stator that thin?

If the magnets are only 4 different thicknesses, somebody got lucky.
Some have 4 mags, 1 pole per face. Some have 2 mags, 2 poles per face. Some have 1 mag, 2 poles per face. Some are long, some short, some wide or narrow, or thick or thin. I have not noticed any standard yet.
Hint: The older and smaller the better, as in under 100megs, have 2 big fat thick neos.

I'm working on a HD gennie now but the HDs are not flowing my way fast enough. Had time to think. There were supposed to be 10 HDs today, ended up with none.
I'll decide the single or double rotor, poles and diameter when I give up waiting for more HDs. That will not be long.
So far there is enough for a single rotor 8 pole.
The number of magnets per pole is 2 to 7 to get about the same 3/8" thickness.
Coil is 3/4" high. The coil hole is 3/8 to 5/8", but most mags are 5/8".