I’m not sure on your question. But I gotta say you have a helluva stable!! If I had 3 BMWs, we’d match. Sorry I’m not help on the seat question. I added a top box and stock seat is good for my wife. She needs the comfort and security of the back pad. Good luck on your search.
‘18 K16GT Option 719 Blue Planet Metallic with matching BMW top-box, Bomber Brown RDL, Denali D7s, Ilium f&r bars with highway pegs
IBA # 63673
‘14 FJR-ES Candy Red (sold)
‘83 CB1100F Blue White & Red (in a garage);
‘83 CB1100F Red White & Black (in a shed);
‘76 CR125 Elsinore Red (sold);
‘73? CB125S Torquoise (sold)