In reply to setting up the stab. After measuring from wing tip to stab tip on both sides and getting that straight, block your wing on each tip on a table / floor until it is dead level and then adjust your stab until it is also equal distance on each tip in relation to whatever the plane is sitting on. I do do this on rare occasions but usually just eyeball it, but I eyeball from further back than 3 feet, maybe 10.

I built a Goldberg Ultimate one time that ended up with a twist in the right bottom wing panel. Try as I may I could not get that twist out. I was going to build a new wing panel but thought I would try it anyway. I flew that plane for 1100 flights that way and even won several IMAC contest over the years.

Bottom lines, do the best you can but don't get your "knickers in a knot"