Im looking at this and I could be wrong but .....I believe what you are asking and what has maybe been missed here, is if you shorten the arrow, would you be stiffening the spine enough to allow you to pack on point weight to get that FOC (EFOC at that point I'd say!)? Am I tracking correct here?
All that aside, I lean toward what GCook said, what you have going already seems like it's be good to go, not sure a change would be worth the fuss for ya, especially if you're accuracy is where you want it to be.
But then again, if you got the time and energy, push it to the limit til you go too far and then maybe real it in again, just for the sake of experimenting and learning. Sure done that a time or two