BTW a resistor/diode taillight run directly off of the dynamo has the disadvantage of no standlight function. For night safety I want a standlight on any dynamo headlight or taillight that I am using. On most dynamo taillights driven by a power takeoff from the headlight the standlight is provided by the headlight circuitry I believe. That is certainly true of the Light On! and Supernova taillights.