The DX6i has a scale on the display screen to show you where the trim setting is. I don't worry about it being a bit off center. It makes zero difference in how the model flies. That's what digital trims are for after all, to let you set the trim easily and not need to worry about it. I don't like having it way over to one side because that means you might not have enough trim adjustment left if something changes on your plane such as a CG adjustment. A big change done with trims also can mean that your servo arm is not square at the neutral setting, which in some setups will cause you to get more throw in one direction than the other.