7 to 12 is quite a big difference! I think you'll find some bows will have better manners with a heavier shaft while others bows are pretty forgiving. I always find 9 - 10 grains per inch to be a happy marriage of speed and forgiveness. Go too heavy and the arrow will seem loggy in flight, go too light and you'll be all over the place with your accuracy.
Allen has a real good release so he can get away with a lighter shaft. If I go that light my bow gets noisy and my accuracy suffers.