Harry here's a couple of concepts to get straight.

The end points on the aux channel effect the gain. The more gain the better the gyro will hold. More gain than you need will wear the servo out faster. More gain than that and the gyro will be fighting itself constantly resulting in tail wag. Not enough gain and the tail will be wandering about.

There's two kinds of gain, electronic and mechanical. Electronic is set in your radio and conveyed to the gyro. Mechanical gain can be increased by moving the linkage out on the servo arm and decreased by moving it in. The ideal linkage distance lets you run the limit pot at or around 100 percent.

The end points on the rudder channel do not effect how far the rudder servo moves, the limit pot on the gyro effects how far the servo can move and should be set the the tail pitch slider can go as far as it can in either direction without binding or stalling the servo, you may and likely will end up with more throw one way than the other, thats fine. The end points effect how fast the gyro will command the helicopter to spin about the main shaft. So if you set the atv's to 100 and the helicopter spins like a blender then lowering the atvs (end points) on the rudder channel will slow down how fast it spins but won't effect how far the servo moves.