I run 11:1 in my 427 with no problems so far. One thing to consider when runnig close to the edge is not advancing timing to radicaly - mine is 15 initial & 32 total. It seems like you could go with a combination of thicker head gasket and additional material off the pistons or combustion chambers and be in the mid - 10's - I think. Sorry, I haven't read all the above posts if they've already suggested this. Don't fret because prior to my rebuild last year I had miscalculated and was running 13:1 on premium for over 700 miles with no major problems. Yes, it was caught and some detonation signs were present but a total rebuild by a professional builder has been done with no cost spared and alls well. I sure miss the throttle response and sound of 13:1 though!!!
Best wishes!