plenty of pro's use these kind of racks. It would be pretty easy to attach rear rack rails to the amp head section and mount a rack fan on there for extra cooling.
T
No temp problems in mine. The racks are quite insulated from the heat of the amp. If you leave it on for 6 or 8 hours (oops) it will get a little warm, but never hot. A fan isn't a bad idea, but I've never found it neccessary.