Lookin' good. Here's a trick I did. I taped pieces of grid marked cardboard on either side of the center beam of my garage door panels (just like yours), leveled them equally on both sides and clamped the tiller tree to the center beam so when I pulled the tiller string down, I could see if the limbs were bending equally. Like doing a grid on the wall. You have to level the horizontal lines carefully, but it worked fine until I did one on the wall.
