I didn't think I'd actually get this far so soon, but somehow I have. I got my APM2 strapped on to my T-Rex 600 and managed to get it in the air. In fact, I've even got it tuned moderately well!
I started out switching the APM from my 3DR quad to the trex frame and began the process of learning how to set up a heli. Being the overbearing fellow I am, I forgot to erase the eeprom so my initial setup was using quad parameters on a heli. After not getting it off the ground, I eventually erased and went through the setup process again and got things right. I got it in the air and tuned a few things and so far I'm happy with how it flies. I used auto-trim mode (ch 7 switch) to level it in the air and that seems to have worked quite well.
The APM board fits nicely in the typical tail gyro place right behind the main shaft. The board is mounted using the Align gel which I've had perfect results with on the quad, and lightweight velcro straps to gently hold it against the gel. No problems with vibrations whatsoever (that I can tell right now, anyway).
I'm happy to have this bird in my fleet once again, and with a second APM (1.0) board on the way I'll hopefully not have to switch back and forth.