That is a great drawing, Kathleen! I have noticed when doing twill on the fly,(as in not planning to do twill but trying it in a "moment of what if") that certain sequences wrapped fine and others didn't. I wasn't really paying attention the first time this happened, but I see now, how it works! Thanks!
When I am not doing double weave, I usually have the center 4 treadles tied up for twill and the outer ones are plain weave. That way I can do it on the fly, so to speak. In such cases where it doesn't catch that outer tread, I just go over or under as a makeshift floating selvage. Works fine as long as I remember to do it and don't get too deep into the "zone" or zen of weaving. LOL.