I initially used the yardstick method and that's what got me into trouble it seems. Maybe it was too flexible. I thought I had it right, but no.
I bought the full size template from Van's, cut it out with scissors, and traced it onto a piece of plywood. I cut it out with a jigsaw, going slow to try and be accurate. I spliced a couple of vertical strips of ply across it ahead of the leading edge and aft of the trailing edge with 4 bolts in each strip. Then I removed the strips and split the template at the leading and trailing edges. Once the strips were bolted back on, I had a template that I could place at any location spanwise on the wing. Yes, there was a bit of estimating involved, but it did show up pretty clearly where I had an alignment problem that wasn't obvious without the template. I moved the hinges to get the aileron where it needed to be and, with the ailerons clamped in trail, re-adjusted the push/pull tubes to get the stick vertical. I don't think I spent more than about a day's worth of work on the whole project and it made a big difference in how she flies.
Originally Posted by az_gila
I could never get any of the templates cut accurately enough to get good alignment on my -6A.
Instead I used two flexible yardsticks laid chord-wise, one on each surface of the wing, and flexed them to meet at the trailing edge. Just envision the flexible rulers as the airflow and get an idea of the top and bottom surface 'smoothness' to this airflow.
As Scott says the aileron is a little 'fatter' than the aft end of the wing so these yard sticks can see if the 'bulge' is equal on the top and bottom surfaces. This method will also check for a top surface skin 'ski-jump'.