I still like the Cinelli binder bolt but using it depends on the binder bolt hole diameter on your frame and if the outer ends of the hole are recessed/stepped up in diameter to suit the Cinelli binder bolt heads. Just looking around the photos of Windsor frames, it looks like the Windsor binder bolt hole is larger in diameter that the Cinelli binder bolt hole and it doesn't have that larger diameter step at either end of the hole. It's hard to find a good photo of this part of a Windsor frame - as you know.

The Cinelli barrel nut can be fragile at the two ends but it does work well and looks much neater and cleaner. It has been in use on Cinelli frames for many years on their 'fast back' seat cluster and Cinelli frames are among the best production frames you can get. But, if it doesn't fit, it doesn't fit and it's probably not original. I just know quite a few Windsor frames have been re-identified a Cinelli frames in the past.

There are so many variations to seatpost binder bolts as there are so many variations to the binder bolt holes of the thousands of frame worldwide. I never overlooked buying binder bolts when I came across them.