Last one to post in this thread wins!

I have a question for those much more experienced than I.

The area of vent grill right in front of the wipers is not as clean inside as I would like to see it before it gets all sealed up. Has anyone ever cut a hole behind the dash, or in the firewall, to clean and seal the metal?

Or, just cut out the vent and put sheet metal in the hole?

I know someone is going to give me some simple, common-sense answer that I should've thought of, but I'm just a dumb Jarhead so help me out. Please!