I made the support in a 10 mm thick plywood piece, but a PVC or PS plate at least 5 mm thick for stiffness may be suitable. This support must be long enough to facilitate handling.
Here is first this support bare. I have provided nylon washers to avoid damaging the paint of the panto.
Here it is with the panto fixed, gently maintained folded by a simple rubber band not too tight. Do not rely on the original hook system, too random for my taste!
The assembly ready to use (Proxxon milling and drilling block, equipped with an XY table and a good vise). The panto is almost invisible, since placed underneath. It is certain that a thinner plate would have made the work easier. Tip: vacuum clean the chips as they appear, otherwise they get caught in the springs and are difficult to remove (lived)!
Here is the final result. I thus milled four pairs of pantographs without any breakage. Sometimes it happened that I just bit the panto's leg shaft because of the lack of visibility. I worked very slowly, with a ø 3 milling bit and 0.5 mm runs. If I had had a ø 4 milling bit at that time, I could have done the job without any horizontal mouvement.
Or maybe a very sharp ø 4 drill bit coming down very slowly would have done the trick.
The newer LSM pantos are fitted with a removable spacer, which avoids this type of acrobatics, but they require filling the central threaded hole… Nothing’s perfect.