Well ... all done, pretty successful
Regulator mounted in place of the battery (with diode
EPP to give a flat mounting surface
Taped to the landing gear, ready to fit to the quad
Flylead attached to the quad
A quick test flight
Got over 4 minutes of in-flight video using packs that had been standing idle for a couple of months. Must time a flight with the camera off, to compare. IIRC the bare quad gave about 9 mins.