Teensy 3.1 I/O Extension

For the still ongoing Graupner mc-17 remote control update project, I need more I/O channels from the Teensy 3.1. By default it breaks out 28 breadboard friendly pins, but on the bottom are another 14+ solder pads with more analogue and digital I/O. By mounting the Teensy 3.1 upside-down, these solder pads become quite accessible:

Teensy 3.1 Extended (bottom is top) Teensy 3.1 Extended (top is bottom)