One trick I found is once you have the trigger bar spring in place and snugged down, back off the screw barely enough to get the spring ends to float just off the wall of the frame. The reasoning is when you tighten it the spring naturally rotates into the left wall, and will try to jump the tracks during shooting sessions. Once adjusted, If you invert the frame you can see the spring riding easily in the grooves of the trigger bar. Then you can adjust the vertical position of the legs as seen in the video.