DIY Belt Tensioner Setup Help

Before I hang the motors on the rig, I decided to test them. Running the Legacy software. I power the Arduino Nano on and the servo arms rotate a full 360 degrees every time. Simhub says calibration complete and I start iRacing. The arms move like they should during the track run. BUT, every power up... the arms want to turn a full 360 degrees!! They'll detroy themselves on the alluminum rig if I hang them. How do I limit the startup movement? I've tried having the hall sensors in different places at startup... that did not work! So close to the finish... Help!!