Wanted to add some more airflow to my RAM/CPU, and I wanted to match the other 140mm in the front, so I modded in a 140mm fan in my 3 empty 5.25" drive bays with some small zip ties going through the holes where you would normally screw it in, and around the drive bay screw slots. I don't get an ounce of fan vibration, even on 100% speed.
I also modded my drive bay covers to be a lot more sturdy, and not fall off. Unfortunately they never stayed in that well, no matter what I did. So I got a couple of plastic clips (I don't know what they are called, my Dad gets them from CA state buildings when he does jobs, and I have not seen them in stores. There are like a plastic clip you would use to close a bag of chips, but with a small metal wire handle that you can remove just leaving the plastic clip part. And these things are STRONG STRONG. They do NOT move).