There is no magic compression ratio you need to increase octane to prevent detonation because the head design plays a role, squish percentage of head area as well as squish speed, ignition timing, carb tuning, ambient temperature, time in the cut, how dirty your cylinder is (cooling effectiveness) etc. You definately can raise the compression ratio high enough to cause detonation, but as to where it occurs, it depends.
I've been doing quite a bit of two stroke tuning research and in one sense getting everything set right for peak performance is much more complex than the often simple approach of x deg transfer, y deg exhaust, z deg intake, set the squish to 0.0XX" raise the compression to XXX psi and advance the ignition Y degrees. On the other hand there are formulas and software that allow you to accurately calculate the performance mods you make before whipping out the grinder and more importantly balance them all together to give you peak power over the rpm range you are tuning the engine for.
