Hi brkl and welcome to the forum,
nice snowoman :-)
Your photo shows vignetting (=dark corners), and I have only seen this when there is something put on the front of the lens which is too narrow (step rings, filter rings, lens shades).
I'm guessing the same lens setup does not vignette on the K10D, which is just what happens with a reduced image circle.
About the lens 'overscrewing', if the mirror does not slap on the lens at the long end, I'd just leave it like that.
Hope I guessed it right,
Georg (the other)
edit:
Here's a ways to check vignetting on your setup before loading the film.