[MiraclePieCo]

I have always suspect that boxing only a portion of the frame and not the entire rail is like sewing a new patch on old jeans. It puts stress on the unboxed portion and that's where all the flex will be concentrated, potentially leading to the formation of cracks.

That being said, if I were boxing an AD frame I would keep the boxing plates running parallel, equidistant from the outer vertical rail, tucking them inside the wider portions of the frame and let the wider parts just hang out. The wide areas of the frame lip seem erratic; it would be difficult and look unsightly to try to follow those variations with your boxing plates. The other option would be to grind the wide spots down so the entire C-channel is the same width, but that seems like a masochistic exercise in pointless perfectionism.

Be careful: frame boxing is a lot of welding. I've seen frames warped beyond salvation by boxing.