Thanks for all the wonderful help! I have another question in my struggle to finish my basement. I have purchased 2'x2' HVAC ceiling diffusers for my vents. They are perforated metal with a solid fiberglass backboard. I need to attach my 6" HVAC flexible runs to these. Do I cut a hole in the backboard? What is the recommended procedure, before I start cutting and screw one of them up? A thorough explanation would really be appreciated. Thanks.

Cut the hole for the size of the A coller you will have to buy. If not enough room to install the flex duct without choaking it off also get a 90 degree elbo of the proper size. It does not get much simpler than this.