Resurrecting an old thread, but wanted to add for those of you WITH Mac 2 into 1 pipes. I made a simple hanger by using the battery box (maybe from a CX or maybe from another bike, cannot remember). It was hinged already. I ran a piece of steel across the top, bending the ends and drilling holes to use the engine mount axle as the attach point. From there I bolted on the battery cage. I can unhinge it to load the battery.
Be warned, this is a tight fit.
Tried to copy and paste from another thread, didn't accept, not sure why. Click the link for the original thread pic.