I have a Wintec Isabell for my straight-backed horse. It fit a very wide, very straight Standardbred, and when I changed horses, it also fit a narrower anglo arab.
Wintec 500 dressage is also a very straight saddle and is adjustable. There are equivalents of both in leather in the Bates range - I am debating buying a 500 and selling my Isabell as the 500 is a shorter saddle for the size and because I have Satin (who is only going to mature about 14.2hh) I'm more likely to be able to find a saddle that fits both her and me if I go a shorter saddle. The Isabell is a HUGE saddle for the size it rides, and mine is older style so it's a snugger fit, and I'm riding a half-size up from where I should be simply because otherwise I wouldn't be able to adjust my position AT ALL. I usually ride in a 17 inch saddle, my Isabell is a 17.5. I've never ridden in the wintec 500 dressage but it looks quite comfortable.