The extra inner rings on the diff pulleys are not needed just the outer ones to keep the belt on the pulley.
You can flip the drive train so that you can move the electronics in closer to the center and move the lipo further out on the battery side. With this setup I feel the car is more balanced left to right with out much more weight added to the lipo to offset the electronics. This is how I have my car laid out I will take a picture when I have time and post it.