I prefer to use the end of the stroke both on the cylinder and steering system to line them up.
Problem with using the center is, its kind of a pain to measure exactly straight across the tires to a leaf spring that may or may not be loaded or to a frame that may or may not be kinked, tweaked or loaded. Point is, if you go to a set stop on both the cylinder and the steering stop, you'll be better off.
So, turn the wheel hard left to the steering stop and hold it, shove the cylinder all the way out, attach the tube clamp or tabs for your tie rod.
Now disconnect the cylinder from the tie rod and cycle everything all the way the other direction and check the alignment.
Adjust from there.
EDIT: Take your time! measure twice and do it once.