FRSky TARANIS telemetry mobile phone holder

I have built a mobile phone holder for my FRSky TARANIS in order to use telemetry with my hexacopter and my mobile phone.
For my galaxy S4 I have used a comercial case joined to the printed piece with double face adhesive band.
The arms and the back piece are from https://www.thingiverse.com/thing:349502.
The knob for fixing the set is from http://www.thingiverse.com/thing:714498
For fixing the set to the Taranis I have used a M5 threaded rod and three M5 security nuts plus a M5 standar nut