Greg
You only did half a job, what about drawing the chrome escutcheon / switch plate that the switch fits in :thumbsup: fitted on the bj8, this has the same cutout shape as Greg's drawing shows. So in theory the switch should only be able to rotate a little.
If its the right switch, being a model 47sa part number 31973k.
yes a star washer might help, I think it should have a thin metal spring plate washer as standard, between the switch and plate, with the bezel fitted on the front of the plate.
cheers Andy