Just from a physics stand point I would guess that the origianal caliper was meant for a certain diameter, putting the caliper made for the larger rotor (if the mounting holes line up) would result in the pads not making full contact on the rotor pad surface. To put in an extreme perspective, if the rotor was the size of a half dollar that pads would be of course way to big, if the rotor was the size of a monster truck wheel the pads would have little effect of doing anything other than burning up into dust. So the effects would be small in physical size but stopping power would have to be determined in an emergency style stopping event before and after modifications. Be Safe your life depends on those brakes working properly!