I run 2 plate style coolers in front of radiator. Is there any reason to not use a check valve in cooler outlet line to keep fluid from flowing back to pan with engine off?

I wouldnt on a GM transmission. It is not needed like on chrysler transmissions, and even then, we remove them on o.e. vehichle because it can be a place that catches trash and hangs it closed.

Thanks. Sounds reasonable.