S Bar owner here and I looked into this not too long ago. The short answer is it depends on the shape of the bar ends and the width of your handlebar. If your handlebar is around 48cm wide then the only ones that will work are probably the ones that do not aggressively curve in. Basically you get more inner clearance (bar end to front tire when folded) with wider handlebars. As far as the bar end length, my rough measurements showed that you can go with up to 16cm long (diagonal to the handlebar).

It is always windy around here and I too would appreciate longer bar ends. I finally decided to go the drop bar route with brakes which is also doable up to some extent. Waiting for funds because it involves more hardware and time. That will be my bike project this fall/winter. A D-Bar Brombton