OK, I found my stitch nob adjustment chart I made with my #1 66 treadle.
I started with the control nob all the way in and stitched a length. Then in the middle of the stitch I measured the number of stitches.
All the way in gave me 7 1/2 SPI.
AT 7 turns out, just before the point the feed dogs quit feeding I got 49 SPI.
I keep my nobs marked with a Sharpie for reference. And due to wear and slack they do vary. But I figure if I started at 6 turns out (28 SPI) then backed it up to 3 out (12 SPI) that might work.
What do you think Charlee?
Joe