When I had a Buell XB12S , I used a Snap-On back brace similar to the backalign as I couldn't fit a rider backrest to the bike.
This worked quite well for me.
I added the non adjustable Harley rider backrest to my 06 EG Standard , and it worked so well that I mounted the same to my 09 Ultra (just needed the adapter bracket which I fabricated).
The non adjustable rest was not proper for me when purchased , so I carefully bent it (cold) in a 20 ton press to move the top rearward.
It took a few rides to get it perfect , but now when my back bothers me , I can go for a ride and come home feeling better than before.
The next thing I installed was the Khromewerks 300515 +2 wide sweepers bars and Kuryakyn ISO grips.
These moved my hand position back so I had to reset the backrest and that was the key for me.
I had back surgery in '98 and continue to suffer from degenerative disk disease , so the the bars and backrest is the only way I can ride over 10-15 miles on any bike now.
All the bikes had the stock seat , so that was the only constant between them.
Buy the bike you want , life is short , make it fit you , enjoy the heck out of it.
Mick