I've got Corbin seats and a Corbin backrest for the driver's seat, which also works for the passenger.
Two things: one, it doesn't cause you to lean forward. You can adjust the tilt on it. but..
two: the back protector on my tech jacket , along with the vibrations of the Spyder, lifts the backrest right out of the seat. Twice, I found it laying on the passenger seat while i'm tooling down the road at 70 mph!
So I gave up on it. I only use it when my wife rides the passenger seat -- she likes the backrest in front to keep her form sliding into me when I brake, and another one in back.
I just got back from putting 10000 miles on it going across the country and back -- never missed the backrest. So long as I have the highway pegs ( from NMN), I could still put my feet up and relax.