So, I thought Snapmarks might be the solution to print PCBs double sided. Maybe my process is flawed.
I created a rectagular template with the snapmarks centered within the rectangle. I cut the template and scored the snapmarks, and without moving the waste piece, flipped the template over and put it back in the hole, and scored the snapmarks on the other side. Now I have a template with snapmarks mirrored on both sides.
I then taped a PCB on one edge in the center of the template.
Engraved one side, flipped it over and engraved the other side.
The resulting engrave is for some reason, off by 3.11 mm on the horizontal axis. The vertical axis is fine.
I did notice during the first snapmark scan the red laser was left of the snapmark, and on the second side, the red laser was in the middle of the snapmark. (about the same distance the engrave is off.)
I did measure the template, and it seems to be accurate on both sides.