140mm didn't work in the rear of the Tripster. The caliper caught the mount so no side to side adjustment.
Go 160mm front and rear IMHO.
The BB7's on Jones demo's I've played with haven't been great. Maybe it's just me but I don't like them. The suicide lever probably didn't help but thats the way Giant spec them.
Too many bad experiences with Avid hydros on Giant bikes as well. Avid sent a memo round saying they were "the best out of box performance" in a disc brake. The next paragraph went on to describe how to set them up and pre-bleed them. Best out of box my bum!