Amazing clip. Not much strumming going on, though.

I guess the tuning is something like
G, C, F, A#, D, G, C, F, A#, D, G

Or are the bass strings stepped down more consistently -

G, B, E, A, D, G, C, F, A#, D, G ?

If you had *thirteen* strings you could go right through the scale with the same interval, instead of taking a shortcut from G to B: it would go

E, A, D, G, C, F, A#, D#, G#, C#, F#, B, E

No, I don't know why you'd want to.