A:Answer Yes I did a horizontal venting for the Broan that we installed in our remodeled kitchen.
Installation instructions do deal with vertical venting and how to mount what they call the adapter/damper on top of hood. Actually above the rear edge of the hood.There are some mechanical steps to afix the adapter/damper to the hood. This is rectangular in shape (about 3" X 10") so final step is to match that piece to the existing duct. Whatever size or shape existing duct is, oval-rectangular-round, you must then match the new adapter/damper to the existing vent. I had to go to Home Depot to find a transition vent to match what I had. Good luck.
