Years ago, when I put new scrapers and upper groove trim into my front door
window opening, the upper part was, say, a half inch too long to fit and I
had to trim it off.

Now I'm doing that job again on a different vanagon. Same problem . I
simply can't fit the entire length of the upper piece in the space between
the vent window rubber and the top of the scrapers. The scrapers, of
course, have a stamped steel form under the rubber and there is no other
way to install them than the way thy go in, so there is no adjustment
available there unless I'm missing something.

If you've done this without trimming anything, how did you do it?

Jim