is 11.2:1 compression too much for 91 Octane

If that was my set-up, and it was already fully assembled, id just drive it and see.
Here in Manitoba 91 is E-10. And based on my sbm experimentation, I have concluded that E-10 is a little more compression friendly. Like was mentioned in post#2, I also ran 205psi. and with a Dc/r just under 9/1,IIRC, on 87E10 at 34 to 36*. Its gone 125,000 miles now, has never detonated at a normal running temp of 205*F, in my S-clone. I put about 8 runs on in total, 4 of them on what many would say, is crap fuel; the 87E-10.As a small block streeter though it may not apply to you. My Wot running is limited to 3 to 5 second blasts, and usually from 25 to 30 mph, beginning in 2nd gear at 2200ish rpm.
I see at least 2 options for your assembled combo, if it does happen to detonate;
1) Timing and timing curve, Obviously,
2) Carburetion
3) Loading
4) Temperature
5) Water/meth injection
-Oh wait, thats 5 things.
-On the other hand, if your engine is already apart and you are in the re-planning mode, different story.