Modular Quadcopter Drone System

I've spend the past few months considering, and experimenting with, various drone designs. For now I have arrived at this H-frame quadcopter.

* Designs consisting of complex monolithic pieces mean that any damage requires you need to reprint/replace large sections. Instead this design is composed of small modular pieces.
* X-frame copters with electronics sandwiched between the top and bottom plate are a real pain for accessibility/maintenance. This design uses a single-layer structure with accessible electronics (or protected only by a non-structural fairing).
* In the early days I spent too many hours printing drone arms only for the print job to fail or for them to fail in flight or during a heavy landing or crash. Carbon fibre is a wonderful, rigid, strong, lightweight material so let's use it for the backbone!
* Hexacopters do not really offer redundancy except in very specific situations. Traditional helicopters, bicopters or tricopters require flight-critical servos so you