I think I got it. I did use the rear bolt on the inside rail; it just seemed to better match the mounting point for the opposite side. The anchor slips right under there nicely. The shoulder harness anchor point didn't leave me much room for adjustment (I had to extend the belt fully), but it all seems to be solid and fitting right.
I would post a couple pix, but the attachment manager just made me its bitch and won't play nice.
Edit: ok, pix.