After I set my control surfaces to neutral with a ruler on the chord length square to the bottom of the wing, I took a large enough protractor, trimmed away the center support and made sure I had the right amount of travel. (see pic)

You'll get multiple ideas here, all great. Even if you use a standard straight edge ruler, you’ll get a rough idea on the amount of travel, albeit it being on a vertical measure.

I used a 6” protractor on my 4*60. Food for thought.