Just glancing at this... a long, long time ago (1978?) I handled what I think I can recall as being an F2 Photomic? Is this what this camera is? For my small hands back then, it must have been quite a haul-up (being confined to a wheelchair with distrophy at that time, since long, long recovered). But a few years later I was the owner of a Nikon F3, probably the next new kid on the block after the F2? Fascinating that the F2 workhorse is still in use and much loved by so many. I vaguely recognised it from the photo in the posts. I haven't seen one second hand for many years so I guess they are rare.
Canon EOS1N ('Brutus', 1993—), TS-E 24mm f3.5L, 20mm f2.8, 17-40 f4L, 70-200 f2.8L
Pentax 67 ('Pentaximus', 2010—) + SMCP 45mm f4, 55mm f4 & 165mm f4LS;
Zero Image 6x9 multi-format pinhole (2008—); Sekonic L758D;
Olympus XA, Nikon Coolpix P7700
"If you're not having fun, then you're not doing it right!"
Your FM2 with the high shutter speed of 1/4000 does have a vertically travelling slit but since it has 1/200 (fm2) flash sync speed and that means the shutter curtain travels very fast and reducing the distortion you wanted to almost none.
Correct. You need a Graphic or Graflex with the slow traveling shutter curtain, use a low tension setting and the smallest slit.