You need to learn to defend yourself against larger males, and this can only be done by training with large males. Shihan is very skilled Judo, Karate etc. etc. and has many, many highly ranked female instructors who would be able to give you different insights.
That style is a traditional style.
You should also check out some non-traditional styles such as Gracie Jiu Jitsu. Yes, it is a lot of grappling/wrestling, but again, in the real world that's the sort of situation you might want to defend yourself against.
I am a short, muscular male (5'8 ,170lbs) who has often used BJJ techniques to dominate men that were 100 lbs heavier than me. That being said, in the past I have been dominated by women BJJ practitioners that were only blue belts (a low rank).