I know a number of guys that run a cooler just like New Interiors posted - and all seem to like them. Tucked alongside the frame rail, that style should still get good airflow - a stacked plate should have a fan to pull air through it.
New Interiors, Have you seen any performance data on that style of cooler? I have seen ratings on the stacked plate style - in terms of trailer weight, but have not seen similar ratings on the finned cooler type. Most guys that use a trans cooler on their rod don't seem to run a trans temp gauge - regardless of cooler style.