I run 91 or 92 octane with Castor 927 @ 40:1
I know exactly how you feel, only a few places *sometimes* have 92octane...so that's usually what I run too.
I had to replace my stator, so I just bought one of their stock wattage stators on an adjustable plate. Advanced the timing +4. You can mod the stock plate to +4, there's a post somewhere on here with pics & info on how to do it....you'll dremel out counterclockwise 1mm for every degree you want to advance. For instance, 4mm would be +4 degrees advance. +3 wouldn't be bad either, like you said; to stay on the safe side...it's up to you, I wouldn't go over +4 unless you have a motor that can handle it. I myself, would suggest modding your stock plate over a degree key, I've heard too many bad things about degree keys. But on that note, I've heard several good things. Never heard anything bad about modding the stock plate or aftermarket adjustable plates.
Ride On!
Led Zeppelin
What kind of compression are you running?