I don't have any technical evidence but I will tell you that I put 24,000 miles on an 03 Mastiff and then over 40,000 miles on an 05 Chopper while living in Southern Kalifornia and commuting 100 miles a day.
This area and into Arizona and Nevada has some of the hottest temperatures in the nation. I've rode through 120 degree temps in Death Valley. Over 110 in Blythe, Laughlin, Vegas and other areas and never had a problem with the motor on either of my bikes.
YOU have to experience riding at 100 mph in 110 degree temps. It's like riding in a blast furnace. I would soak my dew rag and face mask at gas stops and within 2 minutes they would be dried out!
I run my tool bag down between the fwd controls and it's below the VR and oil filter and I don't think it blocks any airflow over the motor.
I run Amsoil 20-50 motorcycle oil and run a pressure gauge and my motor is still going strong with over 50,000 miles on it now.
I would think that if the motors needed an oil cooler they would come from the factory with them.
Just my two cents,
:zz2cents: :zz2cents: