That's not the point, Dave.
I already have a Mustang seat. When I was first shopping for seats, there were some interesting goldwing aftermarket seats for sale. Some of the aftermarket seats are pretty nice. Mustangs and Ultimates were not available.
Since I use a trunk in the winter, maybe a goldwing seat would have worked for winter (minus the handrails)? Don't know.
Anyway, the question at this point is not, "why would you do it?". It is, "will it physically/mechanically fit?". I would still be interested in knowing, just for kicks. Maybe someone else would like to know, too.