Originally Posted by unclearthur
Just be wary with seat sizes - the tree length/panel has to suit your horse because it needs to be unrestricted as much as possible for jumping. Saddleseat saddles tend to be way too long over the loins.
The length of your leg (mainly the femur) governs the forward angle of the flap you need rather than the seat size, which is more relevant to your overall build. Look at it this way - when you shorten stirrups your knee goes up and forward; your seat does not slide back in the saddle. Or it shouldn't, because that puts you behind the horse's movement.
If you can the best thing to do is sit on a selection with different seat sizes and flap-cuts to see what is most comfortable for you, then try to get something as near as possible but which fits the horse. I always say that the rider is fairly important but the horse's comfort comes first :)
Good advice here. Seat size has more to do with your legs than your actual "seat". For example, I'm short and small, but, I have long legs for my size. My seat can fit in a childs saddle, but my legs certainly do not. I therefore typically ride in a 16 or 16.5 close contact. When the seat gets deeper though, like a in dressage saddle, I typically have to move up to a 17 or sometimes even a 17.5 depending on the brand. It's good to sit in as many as possible as there is so much variety among brands.