Compression ratio for 91 octane

[donraye]

I have a burning ( no pun intended) question for someone who is knowledgeable out there.
I am building a 418 and need to make a piston choice. The choice is all about copmpression ratio and what I can go to and still use 91 octane pump gas without any detonation problems.
Someone on another web forum just wrote that with aluminum heads you can go 1 whole step higher than is possible with iron heads and still not get detonation. My questions are:
1: Is that true?
2: Considering I have some monster 210cc aluminum fully ported and chambered CNCed heads that flow pretty big numbers, so what is the maximum SAFE compression I can go to for a 91 octane motor without running into any detonation or other problems.
I do not really want to "push" the edge, but I do want to get as much power as I can for a stereet/pump gas motor.
I had always heard 10 to 10.5:1 was it, but now I hear I may be able to go 11:1 or even more. I'm an old fart so the 10:1 may have been the rule before aluminum heads were even out there.
What's the story with this? What are some of you builders going to these days with no problems.