What data? 10 minutes on a lift running a Mag-Hytec with a clear cover that he modified? Where is the hard core data points to substantiate his claims? Where is the viscosity loss he claims substantiated by data? Where is the third party objective, certified, and repeatable data to show temperature increases by use of a flat back cover? Did he show unquestionably the pinion gear was suffering from oil starvation or an increase in operating temperatures? I will give him this...he is a GREAT salesman and many folks bought into it...He had plenty of data to back up how the fluid was worked and he demonstrated how the shape of the cover affects the flow and coverage of the gears.
No other manufacturer is as open about the design process and how these things work. That's because they likely didn't spend nearly the effort to understand it.
Show me something from afe or anyone else that shows even a fraction of their design thought or even theory.
The Dana/Spicer cover still has a square area on it that bugs me. Honestly, I think ARB might have the best all-around design when considering both flow and protection of the bolt heads. They are just a bit more expensive.