Brodhead Pietenpol Association

I am nearly ready to cover and I am sweating the load on making sure that everything is correct before I cover it and find out that there is something that I did not address. I assembled the three piece wing on saw horses and found it was quite out of whack and released the anti-drag & drag cables and trued everything up again and found that I have to remake some cables again.

It seems that I have had to do this a few times and I am wondering if cable stretching is happening.

How much cable stretch happens?
How do you know how tight a cable is supposed to be? (no fancy, expensive tools please)

Before and after trueing up.

Man, that's a tough one. I can't image only one set of cables would stretch while the others didn't.
How well sealed are the ends of your spars? Could one expand more than the other due to moisture?

I just remade the wrong cables and it true'ed up just fine. I believe it was just builder error.