Eric - Plug Guy

I need some help. Our bumper plug business is growing, but we cannot address the needs of Porsche owners with cars prior to '89.

A recent customer called with a '73 and he wants to remove the rubber bumperettes. We are trying to uncover what's behind them without him having to take off the bumper.

Has anyone been down this road before? If so, what are they mounted with, and how large a hole is left behind?

Thanks in advance.