[brian_]

As an alternative kooling option, I'd thought of installing aluminum sheets in between each module
...but, have them stick out a bit (probably like 1/2" to 1") on each side, essentially adding cooling fins to the pack

That's what typical pouch cell modules have to transfer heat to the thermal management (cooling) plate under the module - in that case, each sheet is bent 90 degrees at the wall of the module to lay flat against the plate. Examples include all of the LG Chem modules without coolant circulating right between the cells: Chevrolet Bolt, Chrysler Pacifica Hybrid, etc.