I'm far from an expert, but since no one else is helping, I will try. I think your 2315s should be OK spine wise. I'm not sure you really need 31" arrows, but if that is the way they are cut, you may not want to change them. I think I would want at least a 125 gr. pt. for a 31" 2315, but if your arrows are shooting OK, then you might not want to change. I'm just not sure what type of cam system the Silverhawk has, and how it might affect the spine of the arrows. Even if the Silverhawk has pretty much round wheels, the 3/39 ACCs would likely be somewhat underspined, especially at 65#. If I recall correctly, there is a guy on here that has a PSE Edge, shooting 2315 at 30" and 65#. He seems to have a very good shooting setup. You might want to do a search for PSE Edge, and see if you can find the guy. Then you could send a PM, and get some more specific info.