Loren, my wife is 5' 2". after alot of trial and error I cut my wifes wenig down bit b<a href="http://s160.photobucket.com/albums/t196/jrm7800/?action=view¤t=100_0040-2.jpg" target="_blank">
</a>y bit until 13 1/4
I think alot of youth ladies really miss an important spec on most stocks, short of a professional fitting. The most comfortable and improvement in her scores was the shorter grip to trigger length as seen on the wenig new american ladies model. Its almost a 1" closer than the factory Gold sporting "ladies" model stock offered by browning. This was the one point my wife had a big problem with the oem stocks.
Just be carefull you dont go to short, my dad says, if your pick'n your nose after you pull the trigger, its to short. growning up the rule was your thumb.
With the gun mounted there should be aprox no less 1" between your nose and back of hand. My wifes gun is short for me, but I have found it is a good length when I shoot sporting clays compared to the same new american stock I have for my self at 14 1/2". Rollins book helped me out a lot
Jeff/Bigbore613 makes a good point. The correct LOP depends on the shooter's shoulder width, neck length, gun mount height and how directly targets are faced when shooting, the stance that is used.
In addition to the above, the correctness of the drop at the heel dimension (distance of the top of the recoil pad below the rib) comes into play right along with the height of the gun mount. They both can cause the same problem - forward lean or tilt of the gun mounted.
Mac makes a great point on the (hand to trigger fit), this is very important to comfortably reach the trigger with small hands! Length of stock, pitch of the pad is usually the tips given. Another less discussed aspect of stock fit is the relationship of the comb and rib or sighting plane. Most people, kids included, will fare far better with a comb that's parallel to the rib. Too much sloping toward the front gives a totally different POI if the shooter leans the head forward more than usual or wears thicker clothing changing the length. The reverse is true of a field type stock which a lot of kids attempt learning shotgunning with also.
There's no such set of numbers which translate into a standard to go by as pointed out by Rollin when it comes to stock fit. Factories sell shotguns using a set of standard stock measurements which really fit no one. We try to adapt to an ill fitting factory stock but it's the kids who will suffer most.