[RC-Monster Mike]

"If the truck does a couple of endos and lands on its lid is that single M3 screw strong enough to keep from bending when the whole weight of the motor is now being pushed to the top of the truck (remember it landed upside down) by inertial forces? The single screw is then just a pivot point for the motor as the back end of the motor is forced away from the chassis."

Not quite accurate. The screw is subjected to mostly tensile load as it pulls the motor against the mount - friction between the face of the motor and the motor mount does most of the work of keeping everything in place. This tensile force would need to be overcome in order for the motor to move off the mount on the top or bottom side(the screw isn't at the edge of the motor, so the 'pivot point' statement is not valid - the edge of the motor can is the only possible pivot point) As a side note - in your example, much of the force would also be in the downward direction(or upwards if the car was right-side-up) - in this instance, both screws would share the shear load, though the lower screw doesn't offer any tension towards the mount. Even without the top screw installed at all, the lower bushing will hold the motor in place (at rest of course).

While I understand and appreciate the concerns(which is why I explained it in the 1st place), I am confident that this system will work perfectly and will not be a point of failure. :)