dan,tack one plate on to the chassis rail,just one tack....so it can be snapped off again....then dip the bolt in some paint,wipe off the excess and push it through the jig to hit the plate,then rotate the bolt to ensure a nice circle of paint....snap the plate off the chassis and drill where the paint circle is,repeat for the other plates and then they will bolt perfectly to the jig...thats how i do mine.

The jig already allows for the 10mm drop.