I purchased a new GE Profile hood w/450 CFM and found out county code limits are 400. I can't return it, and the estimate for a makeup air solution by the HVAC contractor was $1K. My general contractor has received permission now to use a CFM reducer damper to get the 450 down to 400, but I cannot find one of these that will work with a GE 8" round duct. We called GE customer service and they will offer no assistance, saying they do not have a solution nor endorse a 3rd party solution. It appears that Broan NuTone and others no longer have one for an 8" duct or that will work with other manufacturers' hoods. Anyone have any advice on where to find this? Thanks!