This is a very old thread, so not sure if anyone still reads it -- but just in case, I'm pretty certain that the correct tuning is a variant of open G. The critical part, and what is lacking in the above tuning suggestions, is that the B string is tuned down to G to be a double drone string. I have the best luck playing it in DGDGGD and capoing up to the 2nd fret (the recording is in A). However, given Nic's fondness for open C, it's possible he played it in CFCFFC and capoed up to 4. I don't like this as much on my particular guitar, which doesn't hold such a low tuning as easily; but given how much the drone string is flopping around on the recording, it wouldn't surprise me if this is where he was tuned.

The voicings are all pretty straightforward in these tunings, but as always with Nic, it's the right hand that is both unfathomable and inscrutable. Still...hope this helps. Happy hunting, lads!