Been there, done it, got the T-shirt as Peri is built like this.
Stubben - I was OK with these to a point but they didn't go wide enough for her and the shape of the tree is not ideal for broader horses. I had two Romanus saddles, one was custom made and only lasted her 9 months before she got too wide for it and it didn't suit her shape.
Barnsby saddles with the cut back heads and the half-point system work well for this type of conformation. I had a Raven and then a Luxus, both really nice saddles. Barnsby will also custom make at no extra cost. Alas, she got too wide for even the Luxus :sob:
She now has a WOW which solved the problems and she goes well in it. Downside is that you need a fitter who really knows what they are doing and is familiar with all the panel options and what suits the conformation. You also need to understand that they need fairly frequent adjustment at first and they don't suit all horses (or riders). I was pretty sceptical at first when I tried one for my other mare but she went well in it immediately so when I ran into problems with Peri it seemed logical to try her in it.
Another option is treeless but my experience with big wither/wide horse was that Peri hated it and so did my hips.