Chuck,
The third picture, where the vent is shown against the skin is the point of contention.
Longranger,
I finally decided that close to the skin is probably good enough. I haven't done the final bend yet, but I think it will end up being below the edge of the flange. Maybe about 1/4" from the skin.
I had a little trouble getting the vent line bent the way that I wanted it. It would have been nice if they would have mentioned the vent line installation in the instructions. I went back and looked for that step, nothing. I had already installed the outboard rib, but I was able to make it work. But I realized I might have installed the inboard rib and been in big trouble.