Looks a very interesting project and attempt! It seems in the final videos that the rotation of the two arms for the blades is not in unison - is this deliberate?

Obviously on a Chinook helicopter the blades can be individually angled, and this quad design is like having 2 Chinooks tied together. Would it benefit from the mount of the rotors on each arm being hinged to keep the blades in unison per arm, or would a stiffer central arm connecting both sets of 2 blades more aligned to each other help?

I honestly don't know - just an observation from someone with zero knowledge but looks very interesting.

opposite blades rotate in same direction; good overview here: https://ardupilot.org/copter/docs/connect-escs-and-motors.ht...