AMNPS location/smokehouse

[phil allen]

I'm in the process of building a smokehouse. I'm using a 4"x12" vent for fresh air and exhaust. Instead of doing the "mailbox mod" that I've been reading about, would there be any problem with building a box that is able to be mounted and removed that would just cover the lower 4x12 grate? All my fresh air has to enter this area so I would think air flow would not be a problem.