I've got 2 of these DVR2 things, one working at 12v, one at 6. As I have said a time or two, they are the best regulators I have had. Several friends say the same. Work very well for Lucas or Miller gear, in + or - earth. Mike Hutchings the supplier will reply to your note for sure. In the meantime, for 12 volt you leave one wire unconnected as it says on the bit of paper that comes with; for 6 volt you double up the 2 wires. Have a look at the link a10gf provided and it should all be pretty clear. Clearer than writing it out here.
(One very small point for the avoidance of any confusion: - the DVR2 isn't a 'reg rec' - your dynamo only produces DC so doesn't need the output rectifying. They are just electronic voltage regulators/cut-outs. Reg rectifiers can be got - I have one on another bike - as a modern replacement for a selenium rectifier plus zener diode as used with 2 wire alternators. Just as simple rectifiers can also be got - as used with the older 3 wire alternators which relied on the lighting switch to cut in and out extra coils on the alternator for the delivery of more or less juice depending on load.)
If you're not going to have an ammeter, all the more reason to have decent fuse protection as you'll have nothing to tell you what's going on or gone wrong. For 6v, suggest a 15A fuse in the main battery line. Personally, I'd never be without an ammeter on these things, or indeed on any classic vehicle, as they are all, ahem, subject to the occasional electrical foible. Which is why, again and again to the point of boring people to death, I thank the powers-that-were for the magneto . . . .
