HST, you are a monster.
See if a hardware store near you has small metal washers. Open up your controller and look at the plungers and the circle under the keys; the "inner circle" with the plus on it (if I recall correctly) is roughly the size of the washer you want.
Once you have the washers, get two-sided tape and stick them washers onto the inner circle of the keys. This has the same effect as the cardboard mod in reducing the keypress distance and thus sticking, but also has increased durability and an excellent click sound (no, it's not distracting).