Making a fan shroud

I was wondering the same thing. I see louvers on some shrouds and figured it was to facilitate airflow at speed.

However I've done this before and still experience better cooling when moving than when still.

Worst case I can just make a new one with some slots for airflow.

Gotta love people input, "Good job at failing...." with not actual design help.

Anyway, I've seen some factory doors that open with as air flow across the radiator then close when stopped, some are just plastic doors on a loose hinge to a riveted piece of light rubber (I'd use sheet Buna, like 50 to 60 Durometer). At a stop the fan will pull them closed and pull across the core.

My concern is clearance to the water pump snout, based on what I see on my set up. But you're designing so that's probably taken into account.