First not a cat guy, but this should be a mathematical impossibility unless your clutch's center to center is not too short, your drive belt worn too thin, or your secondary is opening too far. The only time the clutch should move that far is without a belt on it. If it is allowed to contact at the bottom like that, then it is not squeezing the belt like it should be and will be slipping the belt at full shift. You should check your center to center and can likely shim the secondary to keep it from opening that far regardless of the spring used, resulting in no slippage. A good engineer would have made this calculation and saved you the hassle. Continued operation will result in failure at some point.
