The solution for my short backed pony was an ancient Passier Baum. My saddle fitter made the back panel more upswept for us, attached a point billet to prevent it going forward, and adjusted the width. Older style saddles have smaller gussets in the back.
I did something similar with a 16.5 Passier GG for a Section C Welsh Cob I took from backing to PSG. As eluded to in an earlier thread it worked for him, and him alone as far as my current herd goes. I sold it after retiring my Section C gelding. I did just get in today a 16.5 Ideal Tonishia Petite with a wide tree and shoulder relief that may work for my guy (homebred Section D Welsh Cob) though it’s going to be close because it’s got gussets on the back, bigger than I’d like. At first I was disappointed when I sat it on his back because it appeared to be a hair too long and rocked slightly but once girthed up and ridden in actually stayed put, he moved well, and when I got off the sweat pattern was in all the right placed, no dry spots and did not extend too far back. Keeping fingers crossed this wasn’t a fluke. The seat despite being built for a youth is generous enough. I don’t know if a 17 inch would work for the OP. OP I hope your saddle search is going well (and/or better than mine).
I love my DP Saddle and I second them with some caution. There are some issues with them, however. For example, they tend to roll, and they require a specific saddle fitter or a saddle fitter who understands their engineering.
I second a British saddle such as a Black Country. I do love my Germania Klasse, which fits my Fjord perfectly. I have had to make some adjustments to my DP Saddle, but it works for us. A friend loves Duetts for her round horses. Thorowgoods are also really nice and super comfy.
