I have a very wide, flat backed, mutton withered mare. Best saddles with wide angles in the tree? Currently my mare has a Martin FX3 w/8" gullet. It fits tight in her shoulders. No pain before or after. Symmetrical dry spots under the pad in either side as large as my hand. But it is creating white spots. Any help would be appreciated!

Robbie Phillips 
He can help you by sending pictures if you are not anywhere to get the tree fitted by him. 

I love his Extra Wide with 40 degree bars on my round, wide backed mare.  

I went from my main barrel horse being extremely high withered and short-backed - went through over 60 saddles on him. Wide, Narrow - he gave ;me an education in saddle fit.

Now, my main barrel horse is like you described.  Had to search for something completely different and at one point I even stopped riding her for several months, unable to find a saddle I could lope circles in without it rolling. I was saddle broke from all the ones I'd tried that didn't work - even the Martin 8".  

I purchased a Black Mesa saddle by L e n B-r-o-w-n.   I finally have a saddle I can ride all 3 of my different built horses in. There are some features that are very different from a lot of saddle makers.  Designed to eliminate points of pressure that most saddles have.  I will say that on the wide barrel-backed mare of mine, I still tweak things like pad thickness and cinch riggin (you can rig it 3 ways) ------ and I would buy another, but it would have a bigger seat (the run small).

But, here's a funny thing .....I bought a saddle at a garage sale a few weeks ago for $50 -- I was going to strip it to use the bare tree in my tree collection (I have just for fun to see how different saddles fit), save the cross conchos, the nice leather latigo, and then save the stirrups - -they are unique and likely worth over $200, but right now they are rustic home decor.  The skirts were curled up and it was covered in mildew.  I cleaned it up and decided to put on my wide mare before I stripped it, just to see how it sits.  Well, I have been riding in it for almost 3 weeks now.  It sits very balanced on her and she moves well in it - and it is my size and very comfortable for me.  I decided not to strip it and find out more about it.  

It's an original 1990 B i l l y C-o-o-k.  I called the company and they assumed it was likely the 6 3/4" gullet, rawhide wood covered tree.  I don't believe that in all the saddles I've ever tried, has one ever been an original of his.  They said their trees are still the same.

The gullet isn't really wide, but the angle of the bars  match perfectly with hers.    Something to consider....