My only issue with the design and install relates to getting the rear derailleur cable to travel under the bottom bracket. There is no longer a gap that can fit the cable guide, so I just removed it and the cable now sits right up against the bracket frame. It works just fine, as it scrapes away at the paint (and aluminum?) along the undersurface. I see no solution to this on my frame.
I think I have a solution to your problem. On my Bike the bolt that goes vertically through the kickstand hole simply did not line up (I installed this on a folding bike). The motor was instead pushed up against the frame as far as it will go forward. when the motor rotates it will push tight against the front of the frame so I put a piece of foam between the motor and the frame. Works great.
To fix your cable problem do something similar but build a cable guide out of something like wood or aluminum for your motor to rest against. and clamp that to the tube.
Alternatively you could simply reroute the cable elsewhere.
Good luck.