Which "clutch" specific Proteks did you find for the 5x11x4? I only found one bearing that size that they offer; a metal shielded "speed." Not that I think there is a whole hell of a lot of difference between the various labels on bearings.

Outside of the first set of Proteks that let go really quick (and I've been shimming clutches for at least 15 years now), the rest have lasted fairly well (1/2 gallon). The shields on the last set came loose but they didnt completely fail. I generally dont wait this long to check them and certainly replace them more often on race days.