I've ran stock setting at about 20IPM lot of backlash on x axis. (on the order of .030" even loading the stepper down) in the end, we ended up upgrading to ball screws from homeshopcnc made to order and supporting the x axis with bearing. I did a thread on this, but it was deleted on this forum. after 6month of steady use, I've been fighting a bit of rigidity issue. (as long as bit is not loaded, it cuts fairly well, but if it gets loaded down at all, I have mis shaped cut, and you can see the spindle move due to flex.