Aaaahhh... antares are my ABSOLUTE FAVORITE saddles! They are amazing and I was so sad when I couldn't find a good replacement to my old one! Antares are a VERY custom saddle so they're a little unique in their sizing. You basically 'build' the saddle to your specifications when you buy them new. All of the 'sizing' is stamped in a series of letters and numbers underneath the flap so you will know how it fits. The seat size is the length from the button on the side of the pommel to the middle of the cantle but the flap length is adjusted accordingly. A size 15 saddle will have a shorter flap then a size 18. But the antares saddle, you pick what size you want, and then exactly how long of a flap you want. Your size will be determined by a combo of your length of thigh and size of your seat. So you wouldn't want an extra short flap unless you were built with a very large hind end and very short legs, does that make sense? :)
First of all, they fit small. I'm about 5"2 with average legs and normally use a 16.5, but in an antares (and most french made saddles) i'm a 17. The flap on my old saddle was a little shorter then I would have liked (it was a 0, I would have liked a 1, maybe even a 2). Because it's a very custom saddle, their shortest flaps are really quite short. I would say that 13.5 is about the length for a 16.5 saddle. What you also want to make sure is that the forwardness of the flap is what you want. Some jumpers want a super forward flap (and they have them!) and as a hunter you wouldn't wnat that. What I would do is get the numbers on the bottom of the flap, and then call antares (their number is on their website) and find out exactly what the numbers mean. Or post them on here and I can tell you if I can remember them all.
(they change them periodically depending on the year) Sorry if that was information overload. My antares dealer is actually a friend of mine now! Lol...
PS I LOVE the buffalo leather... so much longer lasting then the calf or grain leather.