If it was mine, I'd fix the crooked deck (assuming that is the problem), then modify all pistons the same. Shoot for 0 deck and open the dish a little bit, leaving the piston top flat around the perimeter for squish and quench.
Now, to get from 11:1 down to 9:1 may require more material off the piston tops than you are comfortable with...
Trimming .010 or .020 inch off the piston top, then make the dish deeper by .050 or so I would be totally comfortable with. Not sure how close that would get you. Just want to point out the possibility.
