I will be using 4 nvidia 1080 and 4 1080 ti.

Rig dimensions will be 100cm×40cm×50cm.
I will put a normal room vent for airflow between rig for cooling back sides of GPUs.
The GPUs will be fixed with two screws at the top. I dont think it will vibrate.

http://i64.tinypic.com/2z518jm.jpg