I want to build an alcove bed (see Hibernating Dreams: Alcove Beds | Apartment Therapy New York for examples) against the outside wall of our smallest bedroom. The HVAC vent is of course against this wall. I am 99.44% sure that the duct runs perpendicular from the main ducts down the center of our house straight out to the outside wall, in between the floor joists. The idea in my head is to cut a hole through the floor in front of the alcove bed (about 42" from where it is now) and insert some sort of elbow, maybe some sort of packing/insulation behind it. I have a trundle unit only that I purchased from the clearance section of a furniture store. It is a giant stand-alone drawer on casters with removeable dividers such that it can be used as storage or hold a twin mattress. 1. Am I totally misguided? 2. Is there such an elbow to be purchased? Just insert and duct tape? 3. Do I pack something on the now defunct last 42" or so, or just leave it alone? Thank you!