As long as the pad is not excessively bigger than the bp, I tend to think it is ok. But you do have to make sure that the pad will not fly off the bp when in use.
If you're gonna use pressure on the pad, then over time the foam core will weaken as it will be the weakest link exposed to the cookie cutter action of the backing plate.
The photo below is an OMF 6.25" pad that was used on a 5" bp on the PC. I use it now on a 6"bp for polishing aluminum panels with no adverse effect.
Once again I was comparing apples to oranges.
My forum buddies try to keep me in check when I start displaying postitis...lol
Maybe I need to take a page from Setec's playbook and push away from the forum for a minute.