9.0 is a bit too high, you may get away with 6 psi without a problem but it's going to be a matter of "how close do you want to get". As the CR drops, more boost = more power, but the trade doesn't favor heavy, tall gears, low stall or low octane. You can try a DCR calculation to see where your cylinder pressure will be with various IVC points vs. static CR. You'll also see "calculations" that purport to show what total press you get from X CR + Y boost - but they don't. They only multiply (boost + ATM / ATM) * static, which is not what happens. More info, see my site: http://victorylibrary.com/mopar/blower-engine5.htm
Boost is roots, centrifugal, turbo? They produce boost and handle compression and cam quite differently.