9.5-1 is a safe area still capable of makeing excellent power. As a note, in the Crafstman NASCAR truck series, the trucks engine were limted to a 9.0-1 raio and made 700+ HP. Of course there hardware was booo-kooo expensive and modified, but, it was 9.0-1.
Actual ratio can vary on a lot of factors. For a basic street combo, without problems, everyone is right in playing safe @ 9.5-1 as a max. 10-1 (Or higher) is doable, but pump gas has it's limits and other things about the engine that make a higher ratio doable on a street you may not like.
Extra large cam, retarded timing and mixing race gas in with 93 octane just so you can drive it.