Okay here is my plan but I am unsure if it will work or not. I have a section of duct work running next to my load bearing wall. The hvac itself is max 9" below the floor joists and at max 21" wide so basically 9x21" This hvac runs about 40 feet down the wall as it feeds the house. I have an area that I want to finish about 900 sq ft of this particular room. For looks and looks only I want to make a bulkhead around the entire room so it hides and disguises the real hvac. My question is since my span is about 22" wide I'd assume I would have to use 2x4's for the whole thing. If so would I be able to run the 2x4 the horizontal direction or would I go vertical. I'd like to go horizontal as it would give me an extra bit of room to work with on my overall wall heigh. what I dont want is the bottom of the bulkhead to sag due to the weight of the rock. I would think a 22" span would allow me to utilize the across board being run horizonal. I plan on using 1/2" but let me know if 5/8 is what I need. Code requires at least 1/2. Please let me know your thoughts before I start the project. Thanks