core center is the mid point of the ski core. So if you mearsure from tip to tip and find the center then thats the core center. If you balance the ski on one finger and find the point it balacnes, thats dead center or weight center. I usally mount to this as you know the swing weight will be the same in the tip and tail, but on some skis with big differnces in size between tip and tail it can give a weird position. For afterbangs go with whichever you want.