ORIGINAL: Gundigest
My grains perpound is only about 5 grains off, I don't think it is going to hurt my bow. The recomended grains perpound was once6 and even 7.
But if very likely IS hurting your bow. Granted it's only a small bit under the recomended minimum but in a very small way you are dry-firing your bow a little bit every time you shoot it. Over time this can cause cracks in your limbs, bearing problems, cable failures, etc...
It probably won't explode on you any time in the near future, but why risk damage to your bow for just a few FPS?