Breath Scott breath lol
Like Russell has stated, upper return edge, lower no return edge however, I have very little return edge on the upper portion either, less chafing, but that's just me.
There's quite a few ATA (or other) builders that will be chiming in on your build. Don't hesitate to ask us anything.
Follow the leaders, Russell has an incredible build thread for instance, I would encourage you to check it out if you haven't already.