Advanced cooling design!

[LSx_88_Ciera]

This may sound like an off the wall suggestion.
Look into coolers made for water cooling a computer. They are using some different tube design techniques with very high fin counts which increase cooling efficiency. I think you may be served well to run a combo of series and parallel, left and right in parallel and a series of smaller coolers on each side. Does anyone offer an over/under setup for the chargers vs the side by side setup.
I must say I am intrigued by your dilemma.