Another Sinar board is necessary for the rear end of the assembly, to be able to mont a digital camera, to calibrate the shutter speed without wasting too much film, and to use the monster with a small sensor, like my Olympus Micro 4/3 gives a 1620 mm focal length frame, it should be spectacular.
Cutting with the lathe tool and finishing the edge with the ébavureur (demurring toot), makes nice copeaux (chips).
Getting used to milling with the 2 mm tool.
Now I need 8 narrow strips, 4 for the first stage, and 4 for the top.
It takes more time but I've used the metal hand saw to have a strait edge.
Milling the top groove.
Enlarging the inner groove, carefully.
After sanding here and there, and again and again, it fits alright and tight on the Sinar.
The back of the thing, after velcroing both the board replica and the camera mounting plate, ready to go !