Nice!
Those of mine were done with a 55mm Pentax SMC Takumar SLR lens held by hand in front of the digitals lens, Objective to objective.
There are adaptor rings made to mate two 50's face to face, is that what your 58-58 is for?
Been wanting to buy a Pentax OEM extension set for my SLR(film) for years, but they're now fetching 'collectors' prices
(M42 mount)