A perplexing problem with off-road usage. As long as it's there and can get in...it will. I hated my 1/2 shield but at least when I wasn't being dusted-out from people in front, the airflow blew everything outward. Once I got the flip windshield and ran it shut, the negative pressure behind it pulled my own dust back in from behind...so..I bought the rear shield from SATV. Now..finally...having the front, back and doors it's reasonably civilized in the cab...and when I don't have a butt-load of dust to plow through from people in front of me, I can open the flip and have great airflow. So glad I bought the flip because it does get hot in there and like Led Zeppelin says- there are times when "you need-cool-air", and if I had bought the solid shield...I'd be "not a happy camper" at myself.
So, yeah, with the two shields and the doors..it's tolerable...but remember, when you stop all the incoming air you will find that the heat from the radiator will flow back against the firewall and up-over it into the cab. But that can be sealed off too with some foam.