Pairing them up works, in my experience the same as with yellow tangs.
I have my current to gem tangs about 5 and 2 years now, in the past I've had one which outgrew my tank. I honestly can't call them agressive, maybe this has to do with my selection of fish; the only other 'larger' fish are a pair of yellow tangs (which I have for about 12 and 9 years) and two regal angels (about 8 and 5 years). All other fish are significantly smaller (talk basslets, cardinals, wrasses, clownfish).
In a large tank with enough possibilities for the fish to hide from each other and enough decoration which prevents the fish from seeing each other continually, I honestly don't expect more problems than with yellow tangs.
But, of course, my experience is only based on a few specimens. In Germany a famous aquarist Ellen Thaler, who is also ethologist, has kept these fish in pairs. As far as I know, Chingchai is the third person to join the club.
Chingchai: welcome :lolspin: