I use a pipe-cutter on the tubular leg of an old tripod leg and a retaining ring from a Russian lens to make the RF Cam. It must be polished down to the correct length. The retaining ring went into the inside of this one t build of the thickness for the cam follower of the lens.
Amedeo could modify the 58/1.2, but it requires making a new helical with an indexed cam. He did this for the Nikkor 55/1.2. The straight cam that I use depends on the lens being very close to the Leica standard. A 58mm lens requires a cam rotate as you focus, and a cut made into it. I could compute the amount that needs to be cut, but you need a good machinist to make it.