Actually doing a few long ones now.
When cutting either the male or female part, mill out with a suitable end mill fairly close if not spot on. Change over to dovetail cutter, take a pass over the area you didnt last mill and take measurements from that. Great with a DRO.
Made a few toolposts tooled up with specific cutters but normally use the chinky QR toolpost. These are a decent fit piston type and sure are 45 degrees.
If you use 60 degrees you will have to be more critical with each pass of the dovetail cutter sizing the job. A decent fit can turn in to a sloppy fit within a few thou! If theres any play, it will pull in but what about the horizontal plane, will it be repeatably be the same!
Useless with CAD or drawing on pc, might be easier to explain.