I had a nice surprise today. I went to my local home supply store and picked up a nice new register that I can open and close. Well, I didn't realize that the duct work was so shallow, the replacement would not fit with the vent in the open position. Once I got the original one out, and saw how shallow it was I didn't think it was going to fit, and I was right. I'd say that it was no more than 2" deep. I guess I will have to see if I can find a more substantial register that is open all the time, and is shallow.