Your spine should be just fine according to the GT size chart (cut and paste to address bar, javascript:sizingChart() ) I question why you shoot such a light head though. Have you calculated the foc? You may find better arrow flight as well as increased KE with a heavier head.

For instance, I shoot 7595 advantage pro hunters which are slightly heavier arrow then the xt. My shafts are 29.75" so ever so lightly longer and I shoot a 125g head and still my foc is only 10.18%

Judging from what you've posted it appears your foc is only about 5.93% which is off the scale on the low end of the spectrum. A 125g head would bring you up 10.95% and greatly imporve arrow flight. If you want to play around with the foc calculator it's on the GT website http://www.goldtip.com/calculators/foc.asp

As fior speed the only accurate way to calculate it is with a crono IMO. If you shop has one see if you can shoot through it. Once you have your arrow speed you can calculate the ke your bow produces. http://www.goldtip.com/calculators/kinetic.asp

I think the arrows are just fine. Add a heavier head and you'll be in bussiness.