How do you ensure the template/slot is parallell to your workpiece? ... I also wonder about the idea with different templates. Wouldn't it work to just run it with router bits matching the dominos (5,6,8,10) mm and never change the template?
At the moment all I have is one jar of the 20mm x 40mm 6mm thick tenons. My original intent was to scribe centerlines in both directions on the plastic but on the top side, and realized depending on how aligned your view was you might be off a bit. I put a centerline on the wood strips which could be aligned with a line you put on your wood edge where you wanted the slot made. Making the wood strips parallel to the slot just required comparing each end to the screw slots and making them the same distance from the slot ends. Only one side needed that few second to align, and once placed on the wood edge the other side was snugged up to the wood and tightened down.
I suspect the same template could be used if I had 5,6,8,and 10mm router bits. This template is just for the 6mm x 20mm tenons I have using a 3/16" bit which I have. This template is just a quick attempt to use what I have for the tenons I have. As I cut it out on my CNC it is easy to make a quick change to use 8mm x 22mm tenons and cut a second template for a 3/16" bit. I'd have to change to a longer 1/4" bit for the longer 8mm and 10mm tenons that are available,