Bad idea! unless they have another return somewhere else and it is big enough. if not, their system won't last too long.

Thanks. Will leaving it open under the bench be better, or still a bad idea?

Datagrrl,

I'm not sure it's clear that you intend to keep the return "open" by fronting the banquette with perforated metal.

As a second approach, any chance of leaving the left and right ends open or partially open to improve air flow?

My gut reaction is that the perforated metal will allow adequate air flow - certainly no 'hard science' I know of to back it up.

Let us know what you decide!

But they are calling it an AC vent on theirs, pretty sure mine is a cold air return

When the heat or AC is running, is air blowing OUT? If not, it's a return and as long as you have about twice the area of the vent in perforated metal or louvers you are OK.

Just don't block it!