Ya know, it just occurred to me, it's easy to calculate the maximum torque the spindle motor can exert on the tool, which can serve as a guide for how much torque I need to set the drawbar for. Since I'm using a VFD, max torque should be at base speed, in the lowest gear, which is 660 RPM. The motor is 3HP, so the torque is roughly 3 * 5252 / 660 = 24 foot-pounds. So, the 30 foot-pounds I've been aiming for seems like a reasonable target.
Regards,
Ray L.