After over 25 years of playing exclusively 12 string guitar and having played various makes, models & string combinations in that time, my favourite is without doubt my new Taylor T5z-12c; however, recently I tried something "new"!
I have always been aware but never really too bothered about, where the octave G sits in the mix, sometimes adding to that wonderful 12 string sound but sometimes in many tunes and solos sounding completely out of place.
I recently came across John Butler, an Australian player who has recognised the same issue, so much so that he now plays a Maton, made for him, with only 11 strings (single G), so I thought I'd investigate.
After a bit of thought, I have now fitted a heavier (plain/.018) "octave" string but, have tuned it in unison with the concert pitch G.
The result is excellent, no great loss of THAT 12 string sound, but a much smoother transition across soloing & fingerpicking and it seems to suit the whole genre of songs I cover with a much more balanced sound.
Having now investigated further, I have found all sorts of strange and wonderful experiments and re-stringing arrangements on our beloved 12 strings; (which I won't be pursuing)!

I absolutely understand that it's a case of "horses for courses" but, I just thought I would post this for any other 12 string players who may be looking for a way of slightly taming that octave G!!