I can't seem to make sense of the picture and the text at the same time.
Is that thing which looks like a 2.5" shaft collar really a rotating bearing?
Is the CIM mounted to the chassis, or is the end of the gearbox shaft?
If the shaft, do you have slip rings, or just enough slack to take up the number of turns the drum will make, and how do you support the other (CIM end) of the drum?
If the CIM, how is it mounted to the chassis which still allows the drum to turn?