I never need to loosen the knobs in order to accomplish axis tilt. Even without cork the friction between the metals keeps the plate stable. I wanted to apply the cork to have even more friction when using axis tilt, and to hope that the cork will allow the plate to be better secured when using the knobs.
Good suggestion about running one's fingers along the sides of the plate....I do the same basic action with the front "slider" when applying shift to be sure that there is no swing!
I have the cork ( about $2.00 at Michael's for a very large sheet with adhesive on the back ). Will cut and apply to the sides of the front plate. Report to follow.