Here's how I ran my ad1k. The rack I made for it kept it well ventilated. I would unzip both sides of the bag usually half way for extra air. I agree with ethan, heat will take the life out of it so what ever you use, make sure it can breath.
PS: I could not get quite enough gain when I ran 4022>m148>ad1k (switched over to schoeps same show, location, etc, and everything was fine). I could have possibly been doing something wrong on my end, but 4022's are low output mics, and 20db's is all you're getting out of the m148.