I put the Mustang seat on so I would not need a backrest. I'm 5'10" tall with a 30" inseam. I love that it sets me alittle lower and gives me adequate lower back support. On my old Wing I had a Utopia back rest and it worked well for me. When I bought my F6B in September I tried Smart Mount backrest on the OEM seat and hated it. Just couldn't get comfy.
Put the Mustang on in November and love it. Have ridden many 500 plus days and both butt and back do fine.