Im not sure if the mounting hole/bolt alignments is the same across the models tbh, only really messed with the larger drums/22mm variant of piston. Wouldn't it just make for a longer pedal tho due to the volume increase in fluid movement if you did go larger rather than affecting the effort (at the point of bite). You could easily find some comp valves off a KA in a scrappy for less than a tenner i'd imagine unless you need/want to go brand new?