i have a seidon 120XL AIO liquid cooling, mounted on the rear slot of cooler master Silencio 650 (old version).
immediately after trying to type what i meant, i figured it might be better for me to fetch a picture instead. refer to pic below for illustration:
the pic is old (2014 old). i'm not at my home computer right now so i can't take the actual picture, but i gave you the "hows".
alternatively, i guess you could go dig up your toolbox for those really long
bolts screws and screw them into your rear case and jerry-rig-zip-tie a fan to blow into vrm. it should work.
edit: i guess technically they should be called screws. i'm getting more rusty at english -_-
no siggy, saw stuff that made me sad.