Hi guys, you are both doing really well and Im enjoying watching your progress.
Ive just done a set of tool holders for my beast out of steel. Ive seen comments on several sites with regard to getting the dovetails right and there seems to be a bit of concern.... it really is easy to get right... the primary thing is to not remove the material from the machine once its set up and one dovetail is cut. Moving it can add the risk on not getting it perfectly aligned again. Then you have to start doing the measuring using the rods, otherwise you dont.
For the purposes of a tool holder such as we are discussing you need 2 measurements... the minimal width of the dovetail and the depth... the rest will look after itself if you have the correct angle cutter...
This is mine just roughed out... the width of the smallest part of the dovetail is 42mm, the depth is 13mm (its a large QCTP) this gives me a little cleareance against the face of the tool post as can be seen later.

Cut your dovetail until you reach the inner edge on the upper surface and the outter measurement (wide edge of the angle) is 'right'.... automatically... providing your depth is correct. As you havent moved to material from the clamp, they are also parallel... slide them onto your tool post to check...
My only measurements where the depth and the width of the smallest part of the tool post. This is the result, so far, I've done 8 using this method and all fit great.

I didnt use a dovetail cutter but instead a machine called a shaper, but the process and theory is no different.
Keep up the discovery, its looking great.
Cheers Rob