I thought it would be a cake walk to run pump premium 91 octane in my 10.6:1 motor but I've found I can't put in any more timing than 32* spark lead without detonation (lightly peppered plugs)... This is on an aluminum headed, high altitude motor (carefully prepped pistons and chambers, too!) that should tolerate highest compression... it runs just fine but it runs a whole lot better with higher octane and 36-40*

Just a word of caution, you may be able to get away with 11:1 on premium but you'll have to compromise in many ways to get there...

Two cents,
-Chris