I am remodeling my kitchen and am removing a wall between it and my dining room. The duct work for each room is in the crawl space and extends perpendicularly from the existing trunk line to the exterior wall about 20 ft. Both ducts open upward 12 inches from the exterior wall. The kitchen duct opening is actually in the sink cabinet. This duct work and the sink drain pipe parallel each other the length of the kitchen floor, 20 feet. I want to move the duct work away from the drain pipe and then modify the drainage system. Can I shorten the kitchen ducting and have the vent open thru the floor somewhere in the 2-5 foot range from the main trunk line and not screw up the balance of the system too much? I plan on leaving the Dining Room vent where it currently is, 12 inches in front of the exterior wall. This combination kitchen/dining room will then have two vents on opposite sides of the room with open space between.