Hi Klaus!
I'm running a 12s setup with the Rimfire 50cc and 12s 8000mAh batteries. I use gasoline motor standoffs instead of the Hangar 9 motor adapter for strength. I've fiberglassed the firewall, and taken some material out of the battery/fuel tank area to make room. See attached photos.
Congrats on the purchase. She's a fine aircraft, definitely the pride of my fleet.
Best,
Chris