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.
“The photographer must determine how he wants the finished print to look before he exposes the negative.
Before releasing the shutter, he must seek 'the flame of recognition,' a sense that the picture would reveal
the greater mystery of things...more clearly than the eyes see." ~Edward Weston, 1922.
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.