The goal is to keep the tail on the ground. You need to think about what the airflow is doing over the elevator and have the elevator in the correct position for that airflow. The airflow over the elevator comprises propwash and wind. If the tailwind is strong enough you might want to have the stick forward. When you apply power, eg when turning on grass, going over a hill, you might bring the stick back towards neutral, perhaps further.
Tailwheels are most tricky on the ground. There is no hard and fast rule as to where the stick should be, but most of the time it will be back. Can you not feel what is happening?