I didn't look at the vids but I have cut many shotguns stock for the ladies.
The crook of the elbow to the trigger method is a good method for skeet and other games where the gun is already mounted and you don't have to work the action. Doesn't work well for what we do. What I've found for both but particularly for the ladies is the stock should be just long enough to allow the thumb of the trigger hand to be no closer than an 1" but not more than 3" from the shooters nose. Generally, if the stock is longer the crook of the elbow will be extended beyond 90% and because the ladies and youths generally don't have the upper body strength that men do and the ladies also have those protrusion there on their chest that can get in the way, so the gun will be too front heavy. When you see that new shooter leaning way back struggling to hold the gun up that is usually the reason why, the stock is just too long.
Also the stocks on most of the CAS SXS guns are designed for aerial targets. When you point them toward the ground the positive toe of those stocks tends to dig into your shoulder when you fire. This will eventually cause the shooter to let the stock move down on shoulder which brings the front end up. Shot goes high. Savvy shooters will lean way into the shot but that usually doesn't ’t work for the lady shooters. So, now that positive toe is nailing them. For the shotguns besides shortening the stock I like cut them so the pad is about 5 degrees negative. That helps take some of the felt recoil away shooting at our ground targets.
Here’s a good example. This young lady was 11 years old when this picture was taken. This first pic is her with one of the youth size henry 22’s and as you can see she is still struggling to hold it up.
Here she is with a 12ga Baikal SXS that is cut to about 10”LOP with a mercury recoil reducer and good pad. Her stance isn’t that great but she is definitely in more control of the gun.