nfox,
Take a strong look at the PML covers, we stock them and only them because you get the same exact benefits as the much higher priced covers at a much better price. The testing that PML did revealed that adding extra fluid does increase temp drops, buuuut adding way too much fluid doesn't do anything extra but cost more money for fluids. Another thing to consider is the powder coating, while very nice to look at, it is one of the best insulators out there. Why would you want to insulate an aluminum cover that is supposed to reduce fluid temps with an insulator. PML will powder coat for you but don't do it. The stock pan is anodized and will stay pretty, yet it will throw off the heat much better. This is especially true on the transmission pans as they don't get as much air to them as compared to the diff covers.
Call us if you have any questions etc.
Mark @ DPPI