My mini-compressor (CKSA12) is between the air box and the master cylinder (right between the strut tower and the fender). I removed the air intake pipe that comes from the fender to the air box and mounted it there. It fits nice and tight, but i don't like having my air box so "open" now, that i'll probably move the compressor inside the cab somewhere. I wanted to mount it inside the rear most panels on my 4-door, but that was too much work at the time, and i was in a hurry to install the locker and get it working.
If i could live with it, i would have removed the windshield washer bottle and mounted the compressor there, but then there's no where to mount the bottle. It's a catch 22 as there isn't really a whole lot of room under the hood to work with.