For what it is worth : I had at one time a Hoyer 12, and I tuned her three semitones below concert, so that to play in concert she would be capoed at the third.

Hence the top Es were at C, and so on. The third strings I did not tune in octaves, but in unison. I was told by Meic Stevens ( a maestro of the 12 string guitar) that this was what gives a 12 the 'built in jangle'.

Happy playing, and Happy New Year to all.