I dug up the Heligon after years of neglect with the idea to use it on the Z6.
Erik glued a K4 ring with 52mm female thread to the Heligon and with an assortment of adapter rings I end up with the Leica M mount so I can use my Voigtlander VM/E focusing helicoid in combination with the Novoflex M39/LEM extensions rings, focus is now roughly 3 meters without extensions and as close as 25cm fully extended.
It should go to infinity focus with a direct female 52mm to Leica M adapter ring but was unable to find one back then, currently it is female m52>M43, M43>M39 and M39 to Leica M.
Maybe someone has a good suggestion for a slimmer setup with at least one less adapter ring, getting to 10 meters or so would already be a nice bonus