I think it all depends on how close the sheet metal cover is to the vent grill. If it is close enough, I can see it reducing the airflow by about half. And in this weather it needs all the airflow it can get. Luckily, there should be about three inches of space between the sheet metal cover and the vent on mine when I get it done. I have to agree, Dometic didn't think this one through real well. Sort of like having a leaking fuel tank and tying a can under the leak to catch the gas. It just doesn't address the real problem.
Casey
