I have mine stuck to an ABS plastic raft that fits the standard 45mm hole spacing most frames have, that way I can just remove 4 bolts and out it comes without disturbing the actual mounting of the IMU to the platform it sits on. I find double sided servo tape works quite well for the purpose, I use it for both Naza and Super X mounting as well as a lot of other things on multis. It holds strong enough to keep just about anything attached in normal flight, yet tears easy enough so the things I do attach with it don't get destroyed should there be an unintended landing event.
In the case of a TBS Discovery frame you can fit everything between the decks if you don't mind hanging the battery underneath...
I'll take some more detailed pics of the internals when I tear it down to swap the arms over to carbon fiber, that will be soon after the current batch of parts finishes printing.
Ken