I concur, RDL. Buddy had one made for his v7, looks just like the pic, he says it's fantastic. I have sat on it, and it did indeed feel like it would be the cats PJs for long hauls.
They have been doing it for decades. My dad got one for his 78 BMW for our father son tour to the great out west in 1980, I was 12-13. We had a fantastic time from IL to ID, CA UT, and back. The seat was great!