Don't know if this helps answer your question or not...
I used a Nav III mount and modified it for the Garmin Zumo 660 that I have, which is essentially the same unit as the Nav V. I had to add nylon spacers to the mount to make it work with the Zumo mounting system. It did require drilling (dremel) out a much larger hole for the wires to pass through into the stingray.
I don't have a Voice system on my '05, so I can't comment on integration with that, but I did integrate it with a Starcom1 Advance system (wired intercom) that I have essentially integrated into the BMW system. That part was a ton of work, which although it added a large wiring loom, it works great. I did this all right before the Sena systems appeared. If I was to want this kind of functionality today, I'd just wire the Zumo into an aux in so I can hear the Nav etc through the speakers if I choose, and get a Sena system and be done with it...
Hope this helps.