Here's how I did it on my G (hope the formatting works) :
Switch must be DPDT with a center off position. The center position is low charge, no lights. On one direction is high charge, on the other direction is low charge with lights on.
Terminals on the back of the switch :
1 4 2 is the pole for throws 1 and 3
2 5 5 is the pole for throws 4 and 6
Here is my wiring diagram, which uses the switch terminals as terminal posts :
A 1 to 3 B 3 to ground (I soldered to a ring the same size as the hole for the switch)
C 2 to Field of Generator D 4 to Lights E 5 to Battery
The 3 ohm 20 Watt resistor connects between 1 and 2.
Note : A 10 Watt would probably work, but I didn't want it to heat up. When I grounded the field terminal through my meter, I measured about 1.5 Amps, which would be a maximum of 6.75 Watts dissipated by the resistor. As the G only has one headlight along with the little tail light, I actually get 4 amps on the slow charge position with lights on.
I hope this helps ...