Modification of a HITEC 805MG Servo to get more rotation.

[destino]

Greetings. I am helping a colleague with a large movable model. It has a Hitec 805MG servo that has been modified. It needs to rotate further than the stock servo will turn. The 16 tooth gear on the servo is geared down further by connecting it to an 80 tooth gear. To get the rotation of the large gear we need we need to rotate the servo about 720 degrees and then back again. The mod that was done by the constructor was to remove the pin inside the servo that prevents it from turning too far and shifting the control potentiometer that is inside, from the servo gear to the back of the large gear. We blew up the servo by accident (applied wrong voltage) and are having trouble installing the replacement. Is there anyone on the forum who has had experience modifying these servos. The issue that I am having is getting the servo to respond as I expect to the position of the variable potentiometer. Can someone point me to the setup of this type of modification. that is if it exists. I'm programming it with an Arduino. Cheers Peter