Well, 2 things, the mustang seat doesn't change anything for where the backrest is placed. The backrest gets bolted to the rear fender, and the seat still has the ability to come up. And 2, if you can wait a month for the backrest, I can show you exactly how it looks with both the mustang seat and the stock seat since I have both (I only use the mustang now, the stock is for sale) plus I got the backrest for Christmas and will be putting it on when I get the bike out of storage lol
If you don't like the looks with the mustang seat....you could buy my stock seat lol