The single phase idea is not going to work. For one thing no matter how hard you try ya just cant get three stators with 8 coils ,120 degrees out of phase.
I'm curious why not. He can rotate the stators to any position so he doesn't have to index on a certain coil position. I don't think it'll really matter if they're actually at 115° or 123° and his accuracy should be able to be as good as any 4/3 single layer coil stator.
The problem is 360/8=45 degrees
So the distance between any two coils of all three stators is 45 degrees.
If you turned the second stator 45 degrees from the first you are back where you started.
I would go with three phase for all three, line them all up and that will be that.
GoVerticle i have two drawings for you to look at.
These are true single phase, notice how the first one is making no power.
and the second one is rotated counter clockwise and is at a maximum.
There are 10 poles and five coils. All equally spaced.
BUT look at all the wasted material , The coils are three TIMES the diameter of the magnets !
The wasted space between the coils can be better used with three phase ,and the coil diameter only needs to be twice the magnet diameter.