how i am picturing what you are advising, is to basically have a reveresed kind of Jchannel where it sits behind the new osb walls and creates the square look of the "correct" way of installing the ceiling?
Long story short, my order got messed up at Menards and I didnt get the Jchannel in the right color for my Pro Rib metal ceiling install so it was mounted to the trusses without them. A few buddies helped me install it but now i am scratching my head on how to mount plywood or or OSB down the...