I’m just trying to look for a solution, without being an expert.
I’m still thinking that this might be a solution.
The magnetic ring and the AS5311 fits inside the motor with just two 3D printed brackets. See photo. No modifications to the motor needed. At least as long as you don’t need cooling.
Also AMS claims that the AS5311/ring combo is immune to external magnetic stray fields. (I guess that means it will not be affected from the stator poles being close?)
Vdd and Vss can be taken from the hall sensor PCB. and wires from two hall sensor can be used to connect to the incremental pins on AS5311. The last wire remain on a hall sensor. No extra wires needed.
Use rising edge on hall sensor when the motor is spinning in one direction and falling when it’s spinning in the other direction.
The number of pulses from the AS5311 between each hall sensor edge is known.
Even though the number of pulses between each index is not a hole number, and each pole is not a perfectly equal magnetically, it should not matter for a EV built.
9709.037 pulses between each of the 27 poles from my calculation.