I bought some NOS 90s-era rubber floorplate bumpers to assist reloads with the flush-fitting magazines. I am not exactly sure what I was thinking (that they were replacement "extended" floorplates, or they came as a kit that would pre-affix to the floorplates, etc, but the kit arrived over the holidays and all I got was a bunch of rubber slabs with no adhesive. Worse still, the bumper completely covers the floorplate requiring removal of the "glued-on" bumper to remove the floorplate.

My plan is to drill out floorplate release tab holes on these blanks, but the question (for those of you who used such kits in the 80s, forward) is what adhesive works best to glue the rubber bumpers to the floorplate? I am hoping there is something rugged that can be removed without destroying the finish of the floorplate. Suggestions?

I never glued any bump pads on magazines but what I always heard recommended was Barge Rubber Cement.  Apparently the eco freaks got them to change the formula by removing the toluene and new the new stuff don't work.  My only other thoughts on the idea would be the solvent based WeldWood Contact cement or 3M trim cement.

Contact Cement has always worked for me ...

The idea of drilling the rubber pad likely won't turn out well for you as rubber doesn't take to drilling all that well.  You would be better served to find a leather round hole punch for a nice clean cut/hole.

I would use Shoe Goo if you have a tube on hand. It would easily hold up for that work.

I actually wound up using double sided tape for the same thing. The tape is a little thick so it doesn't look as seamless as contact cement would...but it's removable without destroying the pad, and it does work, and work fast.

Take a empty .22 long rifle case and hit it with a Hammer to make your hole.  Works great.  2 sided  tape works well also.