An ATV wouldn't be a good basis for a fuel-efficient commuter and he needs some kind of airflow!
He did tint the top, but 3m clear window film on the rest of the windows would help prevent greenhouse effect.
I am sure that he wants a solar oven (in colder months) or to retain his body heat, but not both.
Does he benefit from having the open front?
I know that the back makes the largest difference by far, but only having fenders cover 1/4 of the tread doesn't seem helpful.
I wish that I knew the MPG of the scooter, the 2-wheeler, and the 3-wheeler.