I personally have not sailed on a Catalina 22. But I think it is nearly impossible to capsize it on flat water unless you really try to, even then Im not sure you could unless it was some crazy wind.
It sounds to me like you need to reef a little earlier than you are.
Letting the boat show her full potential, I assume you are talking about speed? Not how far it will heel over without capsizing. If this is so, then to get the most speed, you need to reef and not let the boat heel as much. Heel does not equal speed. Proper reefing and sail trim equals speed.
Get a GPS and watch your speed as you heel over, the boat will probably slow down. The reason for this is because when your mast lays over your sail are not catching as much wind.