How exactly do you mount your rad if your palcing it in front bottem aprt of the case. I've run into that problem and yer. My case is a Hq-08 if that helps and the rad is a big arse camry '89 heatercore.
I used some threaded stud and bent it to shape, I put some spiral warp on it to stop it marking the rad. This is a shot from the front: I then used a small piece of metal stuck at the bottom between the barbs to stop it slidding out. It's been tranported loads of times to mates house and to LAN's an hasn't budged Just the way I did it