Actually it has a LOT to do with poundage. Your draw length and draw weight will determine what spine you need. Since you aready have the arrows, you need to find out what length they need to be in order to be the proper spine for your set up.

However your correct AMO arrow length is 3/4 of inch less than your draw length.

But if your arrows are on the stiff side you could cut them a bit long to weaken the spine. If they are weak you could cut them shorter to stiffen them up. Providing you don't go so short they fall off your rest when you draw the bow back.

What kind of bow do you shoot, at what draw length and the peak draw weight it is set at measured by a scale, not what you think it is based on how many turns are on the limb bolts.

Paul