I bought an air cushion from BadAss Moto for a solo ride from Philadelphia to Richmond, VA, as non-stop as my tank would allow. It absolutely worked and I was pretty comfortable the whole way.
The problem is that it raises the seat height by an inch and a half or so. I have short legs and my GTS height is about my limit. Hard to remain stable when I had to stop abruptly.
How do you stay comfortable on long, non-stop rides?