Reading these posts through has got me thinking. In practical terms, the movement magnets are horse shoes, correct? I will assume so.
Take a 100 micro amp meter which reads low. Pass the FSD current and take a reading, say 60% FSD.
Take a small neodimium magnet and hold near the outer end of the horse shoe. With that FSD current still flowing, attempt to position the magnet to bring the reading up to 80% FSD. At this point you may need a larger or smaller magnet. Mark the position with a fibre tip, apply super glue to magnet and refit, holding it until secure.
With a second identical magnet,find the 100% FSD level with the magnet outside the other end of the horse shoe and secure.
Now apply a small amount of araldite to both magnets to ensure permanency.
Fine tuning can still be done with the original shunt on an AVO VCM.
Will it work
Les.