High much compression you can run really is dictated by a number of variables, one of the key ones how much ignition advance are you going to run. The other things in the equation are:

Octane of the base fuel
Amount of water sprayed( and a strong enough ignition to fire it)
Boost levels and IAT
Efficiency of the combustion chamber( are you starting with knock-prone chambers)

Anything is really possible if you get the combination right.