so the saddle fits the horse..... everywhere I looked to get info it's all about fitting the saddle to the horse.....how about the rider? What to look for to make sure the saddle fits the rider besides the obvious of the ass hanging over the back of the saddle... how else/what else to measure to ensure a good fit (besides comfort) ?
The leg, hip to knee, needs to fit behind the front edge of the flap. Stirrup bar position can put you in a chair seat (too forward) or tip you back (too far back). Blocks/rolls/padding needs to be positioned so it supports but not interferes. Twist width needs to be comfortable and the balance point of the seat needs to fit too.
I'm sure there's plenty more, but my brain just froze.
Flip a coin. It's not what side lands that matters, but what side you were hoping for when the coin was still in the air.
Being short-on-wide, I got all crazy with measurements for me during my last saddle hunt.
The key dimension is your femur. Seat size doesn't begin to tell you what you want to know.
Core strength seems to matter, too. As in DressageWorld, the longer you have been riding the more "open" a seat you'll like. What that means is how long and flat the valley between pommel and cantle is.
Last, I think you need to know some horizontal dimensions. Three determine fit for the rider:
1. From the knee pocket to the stirrup leather hanging down. Usually you can eyeball this as a forward or straighter flap. But you probably have a dimension that works for you. Again, being short-on-wide, I had to figure this out because most saddles being built now have flaps to forward and nothing bites the shortie harder than not being able to use the knee roll like the tallies can because your knee falls behind it.
2. The distance from the pocket for your knee to the middle of the seat. Again, if you have a long, flat valley back there, you have more room to sit where you want with respect to the flap. OTOH, you'll be SOL if the seat's lowest point is relatively far back *either* from the knee pocket for from the stirrup bar. Both assume a longer femur.
3. The relationship between the pommel and the stirrup bar. This is a small dimension and the variations in it are small, too. In saddles I like, the stirrup bar is pretty close up under the pommel.
Dressagers get way into looking at the slope up to the pommel and trying to pair that with the natural tilt of the rider's pelvis. This is so much harder to put into linear measurements. But you can see the difference between a french bucket like a Del Grange saddle (and also the steep rise to the pommel in many french saddles), and the gradual, but uphill slope built into a County Stablizer.
The best you can do is ride in many saddles and take a look at how they look (when they are balanced on a horse). You'll see the dimensions that you tend to like.
Rather than reinventing the wheel, I usually just tell people to start with Beval Saddlery's Saddle Fitting for the Rider. It's not comprehensive and glosses over some of the nerdy particulars, but it's generally what most people are looking for when they ask this question.
Women with a "rounder" inner thigh (like myself, sigh) are generally a bit more comfortable with a narrower twist (gives the thigh a bit of space), while those with a flatter inner thigh may feel more secure with a wider twist (greater surface contact). This is a generalization, and may not be true for everyone, but it did apply to me.