This mount fits into the back of the Taranis and will hold your Nexus S4 phone. Has room to fit the mini-usb dongle. You can use sticky backed Velcro to attach your APM2 transceiver to the back.
This provides an easy way to use Tower from 3DR (or DroidPlanner) with your Taranis.
Video link: https://www.youtube.com/watch?v=rk2l75YPUVQ
You'll need 3 Screws and some epoxy
Screws: 3mm X 11mm Cap head screws