I ran across this a few weeks ago and was really impressed with the effort and quality of workmanship.
Moving the motor in to the frame got the cg where it needed to be. Now the machine piro flips w/out stutter at the tail. SO, by moving the mass of the tail motor to the CG, the angular momentum is greatly reduced because of the reduced mass at the extremity. And, consequently the system uses less energy to overcome inertia to change acceleration dA/dt (jerk) and d^2A/(dt)^t (snap). Also, uses less energy and processor power to eliminate harmonics to return to stable flight after performing a high angular velocity movement.
These guys are now talking about making the tail variable pitch, adding a tail servo and getting rid of the big regulator you see stuck on the front of the board.
Here’s the thread for those that want to read about it.