Thanks, everyone! I went and tried again and although there's a bit of give, it just does not want to move. I'm wondering if the guy I bought it from modified it in some way? I took some pics of how it looks with the 35mm lens mounted, and the front of the enlarger.
I guess I'm not sure what the different lensboards look like, or why you would want a different one for a different length of lens...but now I see the table in the manual where they list the lensboard numbers. Is it worth trying to track down the proper one, or do you think I might be able to make it work?