Lots of interesting information guys! Thank you all so much!
I've slowed it down quite a bit, and the torque drop off was helped somewhat by turning off the slow start (it wasn't helping much anyhow), but in order to get me into where I want with the speed, I'm still getting some stalling out.
Sounds like the easiest thing for the non-mechanically inclined might be to replace the hand wheel. Unscrewing a couple wheels and replacing the belt seems doable. Unfortunately, my guy doesn't have any idea how to get a new hand wheel or servo motor pulley.
I've got a Nakakima 341L (I'm lead to believe its a Juki 1341 clone) and a Enduro SM600-SP. Can anyone recommend a dealer who might have these parts?