I am assuming you are referring to the utopia add on backrest? It looks like you still have the stock seat.
My suggestion would be putting the backrest money towards a new seat. It hurts ponying up the cash up front but getting rid of the stock seat really seems to be a choice most riders don’t regret. Mustang ultimate and Russel all offer more lumbar support over stock as well as less reach to the bars and the ground for us shorter riders. My ultimate completely changed the way the bike rides and feels and I can now ride all day without any pain. I do have a rider backrest but rarely use it.
I know I am always chiming in when it comes to seat selection but I went from considering selling the B to never wanting to get rid of it. I just hope I can help someone else in the same regard.