My wife just got her RPAL, I'm pretty happy about that, now we can both enjoy the sport. Anyway, I want to get an AR for her to shoot. She has a fairly small frame and a standard length rifle, 18.5in, is ok but she gets wobbly with it after a while. I was thinking of getting a 7.5-10.5 length upper; how would a sbr effect recoil and how short should I go? I want her to be comfortable when shooting.