As Florida seeks to revive its private home insurance market after almost a decade without a hurricane, homeowners are pouring $6 billion a year in premiums into a new generation of small, in-state insurance companies with an unproven record of withstanding a major hurricane. A consumer-oriented rating agency, Weiss Ratings, recently awarded the companies a median grade of C-minus, and even without a major storm to drive up claims, 11 of them have already failed in Florida since 2006, according to state records.