In my opinion, with a long 30.5" arrow, you'd need around a 100 grain point weight because if your draw length is 29", you're pulling around 52# or slightly more. If you want to use a 125 grain point weight, you'd be almost spot on with a 30.5", 2114 aluminum. If you want to use a heavy 2117 at 30.5", it should fly well with a 175 grain point weight. This assumes you've got a 29" draw length. I'm also assuming your bowstring is dacron, not fast flight, your arrows are fletched with three, 5" feathers and you're shooting off the shelf. As you can see, there are lots of variable to take into account.

One variable is draw length. Draw length is very important. With a 28" draw length, you're pulling 50#. The difference of one inch makes a big difference point weight wise with different spined arrows. As an example, with a 28" draw length pulling 50# shooting a 30.5", 2117; you'd need a 205 grain point weight. I suggest you find out "exactly" what your draw length is.

You can play around with this free spine calculator known as the Dynamic Spine Calculator, but all the info put into the 14 boxes has to be "correct". Putting in the wrong info won't give you a tunable arrow. You're looking for a tunable arrow which means you might have to adjust your brace height and/or nock point height. You'll need Microsoft's Excell program to use it since Excell will open the calculator program for you. If you don't have Excell, then download the free Open Office program. Open Office is what I use to open and use the Dynamic Spine Calculator program. Some of the variables I spoke of are in my signature.

http://heilakka.com/stumiller/

http://www.openoffice.org/