Improved version of - http://www.thingiverse.com/thing:735065
The thumb screw is improved for better comfort so you can apply a lot more torque. The phone mount portion can be clipped on and off the transmitter mount. Ears on the phone clip makes it easier to remove the phone from the holder.
The mount is designed around my LG G2 in an Incipio case. Modify the clips for other applications.
The clips hold an OTG cable which in turn holds a 3DR radio. http://www.thingiverse.com/thing:41536
The pieces were printed in PLA at .2 mm layer height and 100% density. The center mount piece is tapped with M3 threads. Printed pieces hold threads well. M3x12 socket head screws hold the clips to the center piece. Note orientation of center piece. The groove goes on top toward front. The clip latches onto the groove.
An M4x45 flat head screw holds the mount to the transmitter bracket. A nut secures the bolt to one side of the arm. The well in the thumb screw holds an M4 nut.