Personally, I would cut an insurance frag from the healthiest area on the first one if the STN is quite prominent. Even with polyp extension you never know, sometimes they can turn RTN on you and it's gone in a matter of hours. I was coral sitting for a friend who had old tank syndrome, and waiting for his new tank, and thought about an insurance frag but didn't bother because it seemed fine, and then 2 days ago it rtn'd and by the time I fragged it was too late. That was after it was in my tank for 2 weeks and had super hairy polyp extension. Fortunately the other 4 acro's of his are fine. Anyway long story short, I'd cut a frag just in case. Looks like a nice piece so it's ok if you end up with 2.
