I drilled a second hole through the brass slug for the LED's cathode, since both ends of the LED have to connect to the Downboy. Wires connect one to the other through each hole. I discovered during that process that they don't use high-strength epoxy to mount the LED - it popped off the slug, so I rebonded it with Artic Alumina when I finished cleaning up the old epoxy and deburring the new hole.
The brass slug's grounded via the large spring that sits between the aluminum battery tube insert sleeve and the slug itself.
The biggest issue I've noted is having to either shorten the negative spring a bit or add an O-ring between head and body to add a small gap, so as to prevent the batteries crushing the Downboy against the slug. (I went with the O-ring as it's reversable.)
I still EDC the light. For its size it's very tough to beat.
oO