As long as you are able to adjust using the handlebar nut and lower lever nut, the cable is probably OK. Its not very likely that it could stretch enough during tensioning to cause a problem. Its much more likely that the new plate thickness is adding up to such a close tolerance that you are having difficulty finding the exact spot needed. Some clutch disk/plate combos are not ideal. Best to use Honda plates/disks and aftermarket (or Honda) springs, or try removing the last friction disk (next to the pressure plate) and readjust from scratch.
