I’m on my second Devoucoux Biarritz and unlike many here I have had a good experience with them- my first one was truly custom made to the horse, including having it refitted on the spot (the saddler from France took it apart and reshaped it in the tack room.) However, the rep who was serving my area of Maryland when I bought my second saddle two years ago is not a fitter. He is a salesman. I’m a decent to good fitter myself, and Devoucoux’s tree works uniquely well on my horse, so I was okay with this, but at one point I was this close to turning around and saying “Backs don’t move like that and you’re trying to sell me a saddle I didn’t ask for.” (I did say approximately that to an Antares rep some time ago: “What you are telling me that you’re going to do to this saddle demonstrates a fundamental misunderstanding of both anatomy and basic geometry.”)
They don’t fit every horse, for sure, but there’s not a saddle on the planet that will fit every horse. If the tree works for your horse anatomically, it works for your horse. If it doesn’t, you are going to make your horse unhappy no matter how you work the panels or what you put under it.
I’ve watched reps from Antares, CWD, Voltaire, and Devoucoux fit saddles. I’ve seen more or less independent fitters representing tack shops fit saddles. Ultimately I think that if you’re going to buy one of these, you owe it to your horse to learn enough about fitting yourself that you can tell if the rep has a clue. Or look for a used one and have somebody qualified come out to look at it on your horse. I don’t know where in MD you are, but Maryland Saddlery used to do this- we trailered a horse over to their store once- and if they don’t anymore, in addition to the pros Sheltona mentioned, may have some other recommendations.