just picked up a used adhoc (thanks for the consult; hope it doesn't suck!). not a light thing at 31# out of the box (size large, standard xo build / pike / flows, etc). though it's got tubes in there currently, and a couple lighter cockpit bits will be swapped in. not too concerned, regardless. hitting 27 on that frame would be a mean feat, methinks.
You've seen my build: aluminum everything, mid weight wheels, 5lb fork, coil shock (ti, but still), aluminum cranks, and no real efforts to drop weight, and it was 30.2lbs if I remember correctly.
Stock they come in at 28ish lbs as far as I'm told. The Pike is about a pound lighter than the Metric I had on there, the Flows are a little heavier than mine were. I think a medium frame is 7lbs with an air shock, so its not a heavy bike. I'm not sure how yours can be 31?
Like I said, I'm dropping a pound by switching the fork and the new wheelset should be quite a bit lighter. I think high 27's/low 28's is easily doable.