P3D Difficulty with Nimslo prints

[penultimate@xxxxxxxxx]

I have tried several photofinishers in an attempt to get two frames
evenly centered on a 4 X 6 print.  None seem to be able to manage this.
The black dividing line is off anywhere from a little to a lot.  Has
anyone found a way to have Nimslo negatives printed so as to see the
frame lines on the sides as well as in the middle.  This would greatly
facilitate the ability to cut the frames accurately for mounting on a
viewcard.  

Thanks,
Duke