What am I doing wrong? We are attempting to install our range hood currently in our kitchen design. The instructions say to use 5" rigid duct, which we purchased. But, now that I am attempting to attach it to the hood unit itself, I can't figure out how. The crimped side of the duct is not large enough to go around the opening, but the straight side has a lot of slop (about 1/2"). I'm certain it is not supposed to go inside the opening, as that would impede the damper. The instructions only state "Connect the ductwork to the damper and seal all connections with duct tape". Is 1/2" slop normal around the opening, and we're just supposed to seal it with aluminum tape? We are installing the Faber Inca Smart http://www.faberonline.com/incasmart.html. It seems like I must be missing something.