Ahhh, the age 'ol saddle fit cunundrum. I have a mare that's very narrow in her shoulders and withers, and then springs out through her ribs. She basically needs two different saddles to fit her. I've taken her to a local saddle fitter, and he said aside from custom, good luck. :) I don't go hard, just stay pretty locally, but I ride almost daily and don't want to make her sore. The mare is 6 this year and in great body condition, so it's not that she's overweight. Currently, I'm riding in a treeless just to avoid pinching her. I tried a friend's Burns 20 tree. It looked like a good fit, but after 5 days I could tell it was pinching as her ears were flat and tail swishing when I'd ask for a lope (same thing she was doing earlier this summer when I figured out my last Merrill by Three Forks was pinching). I also had her vetted last week to double check that her hocks or something else wasn't bothering her. Anyone have a similar situation, or tips on saddles to try? I think I may just have to shim her up in the front? TIA!

Yes! Have a 4 yesr old just like you describe. Has a good wither then gets broad. Check out SHeridan Saddles. THey are kind of made to fit those types. 

I would check out Vernon Purdy / Performance Built Saddles.  Watch his video. They are made to fit/weight-bearing/balance through the middle of the back - and not pinch.

I have a custom treed saddle by him - made for my specific horse (BUT that was only because she was so incredibly wide).  His regular saddle fit another one of my horses like you described fantastically).  Most all saddles sore up my thinner in the front built horse because he wasn't thick enough in the front to bear the front of the bars, then the bottom flar of the bars would not even touch his body. I am planning on ordering another PBS soon as I get the extra  $.

Burns are nice- I tried those on my huge mare....I love the open back with no skirting behind the cantle -- PBS is like that too - among other unique differences that have horse comfort in mind.  (I also used to run in a Merrill, but that eventually sored that horse, too).

Thank you both so much! I'll look into these options!

I had saddle fit problems with my mare, but switched her to a corriente and it really helped. I  would totally recommend them. They fit almost any horse i have tried them on and air very affordable for a high quality brand.