I think it would be worth your time to gain some compression. There is no fast and easy formula to tell you how much you would pick up per point. The easiest way would be to have your heads cut. You will have to watch P to V clearance. Closing up the quench area would do you a big favor but being .015 down the hole there is not much you can do about it.
Why so far below the deck? You are running gas right?
Curtis