With the servo disconnected, work the elevator by hand throught it's total travel, end-point to end-point. (even though it will be further travel than needed to fly) Do this 100 times, or so. If it's going to loosen up, this should do it. Return the servo to operation and place the pushrod on the nearest inside hole that will give you the recommended throw. This will provide less servo strain without over-controlling the elevator.