I took a Splice from the Tail Light supply, so there will be no difference in the voltage going to the Bulb.
If I'd wired it in series (i.e. through the Fan, then to the Bulb), it would probably make the Bulb a little dimmer.

 

A shade over two years later, and it's done it again (I think).
I've not used it much since Sep 2021, only put around 1000 miles on it (I know ) been piling the miles onto my Stelvio (62,500 now).
Went for a quick two-day trip to the Isle of Wight last Tues/Weds with three friends.
Weather was perfect on Tues, had a great ride down to the Ferry, and on the Islands fairly quiet roads.
On the way to the hotel for Tues night, the Dash went blank, no Tacho.
Died a few miles later, as before.
Battery completely dead, it was brand new three days earlier!

Left it locked up in a quiet dirt track overnight, got it recovered to the Ferry Port next morning.
Pushed it onto the Ferry, rolled off on the other side, and locked it up in the Ferry Port Bike shed.

Picked it up this morning.

Whipped the Stator off, looks like new (as it damn-well should!), checks out OK with a Multimeter.

Reg/Rec on the other hand, doesn't.

Multimeter on the Diode Check Setting.
+ve Probe on either of the two Green Wires, -ve on the Yellows in turn, I get a Beep & .482 on two of the three, nothing on the third.
+ve Probe on either of the two Red Wires, -ve on the Yellows in turn, I get 1.850 on two of the three, nothing on the third.
-ve Probe on either of the two Red Wires, +ve on the Yellows in turn, I get a Beep & .470 on all three.
-ve Probe on either of the two Green Wires, +v on the Yellows in turn, I get 1.850 on all three.