["QUOTE FERAL"]

Yep spot on!
This is why when someone asks the simple question of "what compression ratio can I go to" becomes a bit difficult to give an exact ratio. It is very dependant on the design and configeration of the completed engine. Then of course you have all the tuning issues, it can be pretty hard to get all this right based on theory alone. My view is that the theory can be used as a guide but thats about all. In reality the control of points 1, 2, and 3 that Feral mentions can be hard to work around especially considering one big variable can be "pump fuels". My experience over the last few years is that pump fuel quality can vary for a million reasons.
So be a little conservative when designing for pump fuels even when your goal is to push everything to it's limits.