Sorry I did not answer questions sooner, I was gone on holidays.
There was a question about selling kits : I did not intend to sell kits. The design is so simple, people could copy it for very cheap : buy a 20x20 CF rectangular tube at hobbyking, 16mm CF tubes for the arms, and CF plates (or CF/balsa plates) for the four body plates, standard 16mm clamps.
There was a question about the motor/ESC/prop config : T motor MN2213 950Kv, Hobbyking Afro slim 20A ESCs, T-Motor 9x4.5 plastic props.
There was a question on why not using solid CF plates : they are two times heavier than balsa/CF sandwiches.
There was a question on endurance. I did not finish all field test measurements but here's my current results:
-measured 33 min on Lipo 3S 5200 Mah, without a payload and without landing gear
-measured 21 min on LiPo 4S 6600 Mah with the gimbal attached and with a landing gear (full load). 4S is required on full load instead of 3S to be able to produce enough thrust per motor, due to weight increase.
I still have to test in the field a 4S3P LiIon battery pack that should theoritically give more than 30 minutes fully loaded (calculation based on the measured total current consumption when fully loaded), as confirmed theoritically by the following graph, with a 5A discharge current per parallel line of cells (15A total ship consumption to loiter):