Correct, you need a thin slit traveling at a slow speed. In my example in post #11, I was trying to reproduce the effect seen in Rober Doisneau's photo of the man and woman twisted around each other. If you look closely at her feet, and follow the line of her legs, you'll see that they're twisted oddly. It's not as great of an effect as I would have liked to get, but it's close. At some point I'll try this again and hopefully have better luck. I was using the 1/1000 slit, but "hand winding" it so it traveled across the film in about two to three seconds.
I ran other tests using the different FP shutter speeds on my Pacemaker SG and was able to get some bending on the upright poles of the merry-go-round with smaller slit openings, but no twisting of my model as in Robert Doisneau's photo.