In reply to # 3902703 by binky I seen people try to epoxy core plugs in place before. Won't work. You are to smack them flat to achieve a tight fit.
I agree completely...........you have to smack them "flat". The general instruction of dimpling them just reverses the dome shape from outside to inside. "Flattening" the center of the plug forces the edges out. Dimpling puts no more pressure on the edges then the original shape. Matter of fact it could be even less than original pressure if you dimple it too deeply, thus pulling the edges in towards the center.