H80i GT radiator orientation (reservoir top or bottom)?

Common sense tells to not put the reservoir at the top as any air in the system (sounds like i have at least some as i get swishly glug glug noises when handling it) is going to instantly cause problems whereas if its at the bottom you would need tons of air before getting any major problems?



However ive seen a few installs with the reservoir up top and its going to go in my case (380t) better this way.



Could someone wade in please?



Thanks.