PU Truck mag That answered a lot of my questions about these covers. Extra large ones may not make a lot of sense because they disturb the oil flow in the housing.
I watched them all and I'm sticking with the OEM cover. The Banks expose' is quite enlightening. All the fancy covers provide no benefit except expensive bling.
Like Gal said. the OEM engineers know more about their axles than any aftermarket manufacturer. I have to agree with that statement 110%