gpidaho - Lots of possibilities; Epoxy (just a tiny dot) or hot glue are the first ones I'd try; You could alternately epoxy the patch to the front of the RB possibly? Or Duro cement, rubber cement, or even thumbtack the patch to the RB might do? (Tired, couldn't sleep, and not sure I have what you're doing right but think I do.) We used to basically pop a 12Ga light field load open, drain the shot, put a .690 soft RB in the cup, and then crimp the petals all the way down against the RB to retain it in the shell; "Pumpkin ball loads", fun and decent accuracy tho its been since 85ish since I did that {sigh} That might retain your ball too, tho the crimp would maybe change pressures slightly higher it never seemed a problem (I was using good solid shotguns tho.)