[RC-Monster Mike]

Modified motors have timing, which is usually advanced. If the motor spin backwards (if you only reversed the tranny without reversing the diffs, for example), they will run hot and be very inefficient. Running an advanced timed motor in reverse for extended priods of time will wear them quickly as well as provide reduced power output. This is the reason for the UE post on his site. As long as your motors are turning in the proper diretion, you have nothing to worry about.