have you considered mounting the charger to the PSU casing? if you can do this without covering any vents, causing a short or exposing the charger to additional heat that would be good.

I use a much smaller charging array than you, a turnigy accucel-6 and an old laptop PSU which is like 1/16th wider and longer than it. The accucel sits on top of the laptop psu with a bit of an air gap between them.

edit: that's a really sweet setup, pictured above