Why you? Auh shucks, rule number one, heat will almost always be an issue in a cab. Well, I would think about trying out another PC fan for an active intake towards the bottem of your cab. What are the room temps?
I have a cab that is 29H 30W and 19D I have a 175 MH in it and it can get fairly warm in there, I have a 240 CFM bathroom fan from Lowes to pull hot air out, and another little fan in there to blow on the girls, and will soon put a small 90 CFM Dayton fan to bring in more fresh air. Those 90 CFM Dayton fart fans only cost about 30 bucks and are so nice to have around, I have 2 in my main cab for Active intake and also to help suck hot air out of my hood. Well, good luck
Adieu