The upper is more or less exactly as wide as the lower at the tapered end.
Keep working at trying to prove that wrong until you figure out the right answer
I was on a Viewliner a few weeks back, and it never occurred to me that people will insist that the upper is narrower than the lower at the tapered end. I will be on a Viewliner again in a couple of days. I will make sure to take a picture to lay all doubts to rest.
Meanwhile you can skip forward to about minute 6 of this video and see what you think.