DRV8434A: Request for Help to Implement Stall Threshold Mode

Tool/software:

I am planning to use the DRV8434A to drive a stepper motor driven needle valve. For this application, I am not planning to add any limit switches and will need to detect stall with the needle valve fully inserted and fully retracted. I really don't want to have to go thru the training sequence if I can avoid it. I would like to tie the STL_MODE pin high and then come up with a voltage threshold that I can apply to the TRQ_CNT/STL_TH pin that will work reliably. I have two items below that I would like feedback on.

1) For my application, I am expecting the needle valve load to be reasonably well behaved when not at one of the extremes. Do we think it is possible to be able to determine a static voltage for the Stall Threshold that will reliably allow the stepper motor to operate when the valve is not at one of its end points and assert STL_MODE high reliably when it hits the stops? 

2) If we think it is possible to tie STL_MODE high and come up with a static Stall Threshold voltage value that will work reliably, can someone help me work out how to set the Stall Threshold Voltage value. 

Randy Holmberg