This is based on: http://www.thingiverse.com/thing:735065 an awesome design by barneyj.
I modified it to fit the Spectrum DX7s and my ASUS MeMo Pad 7. I use this as a GCS with a 3DR radio.
The pieces were printed in PLA at .1 mm layer height and 100% density. The center mount piece is tapped with M3 threads. Printed pieces hold threads surprisingly well. M3x12 socket head screws hold the clips to the center piece.
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.
I added a v2 version of the DX7s mount with slightly wider gripping arms. This version sits much more secure on the DX7s.
I added a v2 version of the ASUS MeMo Pad mount with a small dimension change to the USB plug compartment. (The cheap eBay USB OTG cables should now fit nicely)
Printed on Ultimaker 2 with 0.1mm layer, 100% infill I used a 5mm brim to hold the parts to the build plate.