its difficult to couple a narrow twist with a wide tree as they contradict each other, but some saddle manufacturers seem to be able to manage it through padding. I'd suggest looking at County as a brand, I'm not familiar with their newer models. You'd probably prefer a long slightly forward flap.
Ask yourself: "Can I do anything about this?"
If you can, do it. If you can't... then you can't and leave it at that. Worrying achieves nothing but stress.
Well, the Passier GG with freedom panels can work but it's pretty close contact which makes it harder to sit properly if your horse is well sprung. Used to ride in one but last year switched out to a Custom Saddlery Coronado (there's a new model which was changed after I purchased mine) and I love this one as the twist sits higher so my leg drapes more easily - the stirrup bars are well situated for a longer thigh, but the seat does run small and the rise can feel a bit to snug in front.
Passier has other models with freedom panel, so check those out. They are known for narrow twists. The trees seem better for a horse with a bit of dip behind the withers rather than totally flat back.
You could also contact Custom Saddlery, send them tracings and ask which models would work for your horse then you. If you can get one of their people out, you can try all the saddles and have it fitted. I tried the Wolfgang solo and although I loved the exterior thigh blocks, they were angled in too much at the top and didn't allow me to post through. The Icon flight was nice too but didn't fit my horse as well as the coronado. Love the buffalo hide as well.
If you can manage the pricing, you can try various Hennig combinations to see if you can find one that works for both you and your horse. I have short thighs and need a narrow twist. Found a medium Hennig that works. Just tell the reps what you need and they may be able to find one that will work for you.
I have GIANT horses (the little one, at 17 h, is more wide than the big one, at 17.2) -- I had a County but it eventually wasn't a great match when my younger horse matured....
now in an Albion, love it, fits them, they need a wide tree, I need a narrow twist.
I tried a Custom (maybe the Steffen Peters model?) -- fit the ponies great, but I felt like I was straddling a small car....
Proud owner of one Lunar acre! (Campanus Crater, The Moon)
Welcome to the club...
There are quite a few saddles that will work, but the funny thing is that for my wider backed horse a flocked Wintec Pro fit him and me better than the uber expensive ones (my thighs are very long and this saddle works well enough--nothing seems to be perfect for my long thigh).
The other thing to consider is the rise at the front of the saddle. I rode in an Albion and the rise caused nasty chafing. They do run wide for the horse. Would suggest going a bit large for the rider to avoid hitting the front.
Trilogy Verago. I too have a very long femur and love my Vergo. Keep in mind that if your leg is really long you will need a larger size saddle regardless of the size of your rearend. I ride in a 19 inch saddle.
What has always worked for me in the past when I am saddle hunting is to go sit in as many saddles as I can. I am fortunate to be within 2 hours of several tack shops which carry a large number of saddles. Sit in them, squirm around, move your butt and find the one that lets you sit in that "sweet spot".
Then I usually take the three that I like best home and try them out, all carefully wrapped up around the stirrup leather etc. so they stay pristine. See what fits on your horse and how it feels. If you are lucky your will find one that feels as good on the horse as off. You can tell if you need a med-wide or wide tree, etc. and if some minor saddle fitting may make the one you like fit. If not, move on.
I just bought a Passier Optimum and love it. It has a very narrow twist, allows plenty of room for my hips to open up and the leg to fall down where it should. I also have a very long thigh and they usually have extra long flaps. it fits my 17.2h gelding to a tee but he is not especially wide. A med-wide fit him well. Good luck.
I second the Trilogy Verago! I'm not very tall (5'5") but I have a crazy long femur and prefer a narrow twist. My horse is also not super tall (16.1hh) but is wide. This saddle is fantastic, the reps are super helpful and my horse goes so much better than he did in the same tree size in a Passier GG.
I would second several of the options here. I started in a Hennig, horse hated it. Then rode in my trainer's County, which I would've bought had I been able to find one with the right combination of stuff. Eventually settled on a Albion SLK, which after I rode in it for awhile, like even better than the County.
One thing about the rise as someone mentioned. SLKs have a couple of choices, including a Low Head and a High Head. I believe that the low head rises slower to the pommel, but might be a problem if your horse has a prominent set of withers.