From anti-rotation tab noob to pro in such a short time!
Thank you, dear repliers!
I will experiment with the possibilities. It seems to me that leaving the tabs on and drilling extra holes would be most robust and no visual impairment as the knobs will cover the holes. Although, it could turn out to be far too much work. I have 50 potentiometers only on this device. Then I will try out the various washers. 