Hi Joe,
The DGDEBD tuning you mentioned is only a half-tone down from the one I used ... put the capo on the third fret instead of the second, and it's the same. I used the tuning I mentioned because (a) I trust John McClellan to follow through on this sort of thing with Chet (he used to visit Chet pretty regularly) and (b) going the DGDEBD makes the third string even harder to keep in tune. It's hard enough to keep it tune using the a-flat 6 tuning. I had noticed in playing some in the "Tommy Jones tuning" (sixth in D, third in F#) that running the third string down even a half-tone makes it hard to keep it tune.
But, other people can worry about what key Chet Really played in: G6 or a-flat 6. To me the important thing is to go ahead and tune it whichever way and then experiment, to see what it takes to get the familiar chords, and to see what you can do that you couldn't do in regular tuning. To me, there is no trick involved in learning how to use alternate tunings: it's just a matter of enough fooling with it until you get comfortable with it.
The only alternate tunings I've fooled with in the past few years are Drop D and what I call the Tommy Jones tuning. When I was younger (like 35 and 40 years ago), I used to play in G tuning a lot, Drop D alot, and probably a couple of e-based tunings (it's hard to remember). I also liked to occasionally string one acoustic in "the Nashville Tuning" (Google it for all sorts of descriptions), which is basically just a substitution of tenor strings for the four bass strings. Using alternate tunings in that was really cool. Bottom line: I did so much of it that it became second nature to me. Now, even though it's years later, I find it pretty easy to learn how to piddle in a new tuning. But that's because I put in so many, many hours tinkering with it in the past.
As to the Godin, it's a Multiac SA with Nylon strings. It was signed by Buster a few months before he passed away, and I'm told by his girlfriend at the time that it was the last thing he ever signed. You can read a tad more about it here:
http://www.dkeener.com/music/my-godin-c ... r-b-jones/Hope that helps.
Bruce