Homebrew PCBs

Hi,

I'm ramping up doing home pcb production using photosensitive pcb with a CNC machine contour-laser-plotting.
Single side works great, now I want to move on to double-sided pcb. One of the advantages of CNC-contour-laser-plotting is that the artwork-to-machine offset is perfectly reproduceable, so I was thinking to predrill 3mm mounting holes in my eurocard-size pcb stock using a drill template. 

So I need to mount registration pins on the CNC machine bed. I wonder what would be good pins for this purpose. Ideally something that can be tensioned while maintaining center. Maybe similar to the pushpins used to hold a PC CPU heatsink. Or is just a round 3mm pin good enough? Ideas? 

I'd like to use the same holes as guides for solderpaste stencil creation and application.

thanks,
johannes