Great thread!! I, too, have been afraid to force them off in any way for fear of breaking the glass. So....I have had a mix of new and old ones on the coach.
I will now go bravely forward and try the PB Blaster.
I used small pieces of rubber to create a tighter seal on the ones I have been able to replace. Does anyone have any other tricks they have used to get the new clips to grip the glass and stay put?