ORIGINAL: KodiakArcher
31 in. draw or arrow length? If it's draw then your arrow is likely longer. What draw weight? If it's up near 70 lbs. and over 31" you're going to need stiffer than a .340 deflection shaft. Shaft weight can be irrelevant of spine deflection but generally a stiffer shaft weighs more (given that the shaft is of the same model from the same manufacturer).
I agree with what most are telling you. You need to go to the 340 spined shafts and not worry about the weight. My Draw length is 28.5" and I shoot a 27.25" arrow, so your arrow is not necessarily longer than your draw length. It just depends on how you are set up
Dan