I did a little more work with the new servo motor conversion.
After looking over the modification noted above I decided to try and change the arm ratio.
I drilled a series of holes in the side of the treadle and reinstalled the "throttle" arm link. This give a much more progressive speed increase, however it still requires a steady foot. I don't have any problem with this as I use a foot pedal with my TIG welder and I can use either foot with equal ease. I think I will add a little spring tension to give a better feel to the treadle. It will be stiffer and more like the TIG pedal. Just a personal preference. For reference my link hole is 1 3/4" from the center of the treadle pivot.
Someone mentioned sewing thru 8 layers of vinyl. So I tried this after practicing running straight stiches and some curved ones. I began folding the test piece over and running some more stiches. I also tried slow and faster rates. Eventually I got to 8 layers and even at the very slowest speed the machine will plow right thru and pull the thread tight. High speed is no contest. I couldn't fold the piece up any more so I just added a top and bottom layer and it punched right thru again. That's as thick of stack as will fit under the foot on my machine. This is with the 90mm pulley. I was going to get the 50mm pulley but I think I'll hold off and see if there is a need.
Love this servo motor!!!