Update: I've tested the light (a re-wired hanging Schmidt Edelux) on my morning commute. I disabled my current dynamo light and plugged in the Edelux with ~3 feet of 28awg wire. I rode about 15 minutes with the light on (short commute). At the end of my commute, the wiring felt as cool to the touch as the unused wiring to my disabled light. I suppose I should test the light more thoroughly, say for an hour or longer with continuous use. But so far it's very promising!

The reason for rewiring the Edelux is because when Schmidt introduced their "hanging" or "inverted mount" Edelux, they disabled the taillight lead because its location would have allowed water penetration. Their solution was to remove the taillight lead altogether. They expect buyers of their $200 light to install a separate taillight switch elsewhere on the bike (inelegant IMHO) or just use a battery taillight. They have the 3mm coax cable that goes from the dynamo to the headlight entering the inverted light through a 3mm drilled hole, sealed with glue from the inside (a crude but effective technique, IMHO). I wanted to keep the look of the svelte 3mm coax cable but needed an extra conductor in there to tap into the taillight circuit (which is still there on the circuit board, just not used). I had wanted to ground the circuit board to the aluminum headlight housing and re-purpose the coaxial braided shield as the main dynamo hot lead, and repurpose the 22awg single conductor for the taillight. But internally grounding the circuit board to the light housing was not possible. My challenge was to find 3mm round cable with three conductors. This limited me to the twin conductor 28AWG with braided shield, sold as line-level audio cable.

I'll post photos of the rewired light soon...