I don't think too many women are quite that small - though maybe most can only take 7" or 8". I know that if I relax and position my hips right, I can take 9" balls deep - and I feel it slide >past< my cervix, not into it. I have seen some info online, about how that works, I think a "cul de sac" past the cervix that can expand and take more under the right circumstances...you should look into it.
Also, when I "bottom out" at 9", it hits something entirely different that sometimes - especially if I'm riding "cowgirl" style - gives me these mind-blowing, crazy, out of control writhing orgasms
(0ne of the reasons I'm so interested in finding really big guys)
Lanie