That is likely caused by your undercarriage being slightly misaligned. Don't worry about it and it has nothing to do with the wing stab alignment.

Here is how I do my wing stab alignment. Mount the wing and measure from the rear of the fuz to each wing tip, adjust till they equalise if required.

Now dry fit the stab and measure from each stab tip to each wing tip adjust till they equalise if required. Mark the stab with a non permanent marker.

Now eyeball it from the rear. By moving your eyeline up and down you can check if the stab tips kiss the line of the wing at the same time. If they don't steal your wife's emery board and adjust the stab slot till they do. Glue and check before the glue sets.