I have to be honest - I grabbed this saddle because I thought the flaps would be too short and it would be a nice comparison with another saddle we brought along for our Real Life Rider photo shoot. It came from another professional who is shorter than me. Turns out it was a perfect fit for both me (ok maybe I can use a 17.5") and our demo equitation horse, Common Sense, or Sarge. So lets look at this saddle in more detail.
Featured is a full buffalo Antares Connexion, with a 17" seat and a 2N flap. It has M15 (standard) panels with no specialization, on a standard medium wide tree. I am 5' 4" and wearing size 30 Tailored Sportsmans. Sarge is a 16.3 hh warmblood who wears a size 80 blanket and a 52" girth.
Looking at the first picture, you can see the flap is perfect for me. My thigh is behind the thigh blocks, my knee hits the middle to lower third of the knee flap and there is some space visible between the edge of the flap and my knee. Looking at the bottom of the flap you can see it hits me on the widest part of my calf about a third of the way down, giving me lots of contact with the horse's side. Now, if I like a smaller seat, which I do, the seat is great. If I wanted a little more room to move, I would need to go up a half size.
Now let's look at the fit on Sarge. Although a big horse, Sarge has a pretty standard back shape that the standard Antares panels fit perfectly. Looking at the photos of his back you can see that although he has some pretty big shoulders, he gets narrower and slopes in behind the shoulders where the tree points will sit. The wither is moderate and the back, although long, has a gentle rise to it towards the hip. If he did not narrow behind the shoulder he would need either a wider tree, or thinner, sculpted out, panels or some combination of both. If he was more concave behind the shoulder he would need a panel that is more built up under the tree points to support the saddle on either side of the wither. A flatter back would require thicker panelling behind.
In the side view photo with the saddle on Sarge, you can see the pommel and cantle are level, and that all visible parts of the panel are in contact with his back. When I ran my hand under the panels there was equal pressure on all parts of the panels and when we girthed up the saddle, the pressure remained equal in all areas and the saddle didn't sit down onto his wither at all.