Me personally i would not go over a 9:1 static on an engine you are going to run 89 octane in.... But like the others pointed out there are so many factors that can make or break this combo.
To add to what is allready mentioned.
Make sure you can keep it cool ,,,180 deg max... this will keep detonation down..
Make sure you have the correct heat range plug, and the correct timing curve.
Deburr everything in the combustion chamber,,,,,
The bad thing about running close to the edge is if you get a bad load or 2 bad loads of fuel and your not paying attention to whats going on you will have problems....
Learn to read the plugs, You might not hear the detonation.....