If you want most spine charts to work right, you better have the right arrow length. They don't go off arrow length, they go off draw length to get the length of your arrow and determin the spine. Especially Eastons chart. There is no provision for shooting a longer arrow( which would be a weaker spine by the way) There is however a provision for shooting shorter arrows, use the overdraw selection.

According to Easton your arrow should be 1 inch forward of the the point where your arrow contacts your rest. And if your rest is in the optimal position, that point should be right above your grip ( torque effects the arrow less when the contact point is above the center line.). This is the same place you measure your brace height, power stroke and true draw from. So basically your arrow should be 1 inch longer than your true draw. Or 3/4 less than your draw length ( amo draw minus 1.75 plus 1 inch). This will give you the correct arrow length for most of the charts.

Or you could use a program that calculates spine, like The Arrow Program. It will let you choose any length arrow with any draw length and tip weight.

One inch of arrow length will effect arrow spine, so if your arrows are two inches longer than they should be when you use the charts, what it says will be spined right, will be weak.

Also Keep in mind how much the different bows vary in performance now. If are shooting a bowtech or something simular I would pick arrows that spine about 10 lbs heavier than your actual draw weight.

Just my opinion any way.

Paul