I’m pretty sure the 28mm fits the 6480 with a single cork wrap and no shrink. If you have shrink on it as well, move up to the 31mm.
It’s always best to bring the rod with you and try them if you aren’t ordering by mail. There is some variance between manufacture
Big issue i am with orginal clamp set up is that screws dont enough ckearance to fit well around the blank
The butt sectiion is wide in diameter while the reel seet assemply is narrow in away that the screws will rub against the butt section