I need a board at the rear end of the thing, to hold a digital camera so I can try to calibrate the speed of the shutter.

It's bigger than the Sinar board, because it must fit the below size

Cutting with the jig saw.

This completely worn lens will give an important mechanical part.

Very happy to have the exact 46 mm hole saw, no filing needed, it'll be clean.

Drilling the 2 mm holes, the original screws are too short, hopefully I had some nice 10 mm long M 2 stainless steel screws, and the head fits perfectly in the baïonette's holes.

Nearly ready.

That beautiful purple bungee is quite strong and will have to stand important stress, so il must be firmly held in position, those M 6 pythons are going to be perfect. 

Ready !