Finally bit the bullet and fitted a Wunderlich screen to my XCountry. It's not huge, miles smaller than the acres of plastic that is a GSA screen, but it is surprisingly effective in taking the windblast away from my chest. Definitely an improvement.
I can now be certain that the seat is comfortable for 100 miles but not much more, and that it gets very hot underneath it.
I can now be certain that the seat is comfortable for 100 miles but not much more, and that it gets very hot underneath it.