In my opinion (and it ain't worth a whole lot) the amount of centershot a particular bow has is the primary reason it would require a stiffer/weaker shaft. You could build two bows with everything identical except the amount of centershot, whichever bow is cut closer to center is either gonna need a stiffer shaft or heaver point weight to get good flight.
Also the "rules" of bareshafting that deal with nock high, low, left, right works great until you get way out of whack, meaning that a shaft you though was too weak is really too stiff or you get nock high flight, but the nocking point was really too low. The old Easton Arrow Tuning handout summed it up that if what you tried didn't work, do the opposite. I NEVER cut off a bareshaft until I have verified it through changing point weight. Of course, the arrows I shoot have screw in points, though.
David