Originally Posted by Road Fan

The SA tensioned leather flexes a lot more than Ideale, Brooks, Gyes, and Rivet. So those four depend more on shape (including sitbone and mid-saddle widths). The SA works like a parallel pair of hammocks, which flex independently. They stretch, but are intended to be incrementally tensioned sequentially over time. I have one pretty old one and it clearly seems to have stopped stretching, after about 2 cm! The wings look wide, but they haven't been a problem for me.