Everything I have seen in this topic is right on!
I only want to add, as a former professional bicycle assembler, is most of our bikes were not designed for the speed and stress that a motor adds. Careful inspection of the bicycle components is just as important to safety as inspecting our engines for loose bolts and screws.
Wheel nuts, pedals, seat post clamps, stems, and handle bars are all susceptible to becoming loose from the vibration of our happy times engine. You have not lived till a pedal or front wheel comes off at 30MPH, and you might not live after. So check everything before every ride.
I am a MoteredBike-aholic, and proud of it, but I never motor without my brain bucket!