This morning I depopulated the eight degree rotor to put the magnets on the ninety degree rotor.
On the new rotor the magnets fit well in the slots, but they are not "jammed in" tight. They need some help maintaining their position. So I wrapped the perimeter with electrical tape for a test spin.
The electrical tape didn't last long, but I got a few spins in. The rotor doesn't have the strong cogging like it had with the other two rotors. It is much easier to start and spins longer with when you give it a spin. Then the electrical tape tore, and bunched up in the clearance between the rotor and the stator.