Myself and a few others on this server and elsewhere have been having issues with very high sensitivity on the GCC triggers. Even the slightest analog press can cause misinputs that never happen during play in Rivals 1. Just searching "gamecube controller sensitivity" will bring up results in this server of people with similar issues.
A good solution might be to just let the user decide the sensitivity of analog triggers (on all controllers, not just GCC) within the "sensitivity" menu on the CSS.