I saw a E5 this past weekend that the builder had not bothered to sand his frames. The frame rubbed through two of the ESC to motor connection wires as well as the backup battery connection wires and burned a hole in the frame. Sanding the frames is important, as is a good wire routing strategy. Carbon fiber is conductive, keep this in mind when routing wires and even though electric powered machines have much less vibration than nitro powered machines vibrations still exist. Vibration coupled with rough / sharp carbon fiber edges will eat through your wire insulation quickly. Paying attention to small details like these during the build saves time and money in the long run.
Rich