I am naturally fast. I just need to work on my endurance.
Think preloaders tend to see small women and think "Oh great, another one who's gonna need a spot in small sort". Or, "Can't wait to have to help her pull anything over 50 pounds". If you're 110-20 pounds (or have b*tch legs like @D. Randall Blythe), you're just not gonna have an easy time keeping up with really heavy/heavy-weight flows. It's not a knock against small people at all. It's just a physical reality. I'd rather be small and pretty than an ugly box ox, myself.