It finally happened…I knew that it would. The other day I aborted a take off at a new LZ and ended up taking a knee. Unfortunately, the thin carbon fiber loops on the bottom right arm end broke. Since I have a batch 3 with the super strong injection molded connectors, I designed a repair to allow me to retain the original hoop connector. I downloaded the .stl of the arm from GitHub and chopped off about the last 3 inches of the end to use as a starting point. (Notice the triangles in the second picture from expanding the bit of arm in TinkerCad to 45mm 
) Here are the results:
Here is my .stl file:
arm retrofit v3.stl (117.3 KB)
The M3 bolts that go through the injection molded hoop connector are 25mm stainless steel, and I purchased them from https://www.albanycountyfasteners.com/ For that matter, I have replaced almost all of the M3 and M4 bolts on my X4… the salt water at the beach was causing the steel ones to rust.
Happy flying!
Bill