Deon, sorry if I came across as critical, I wasn't trying to be. I think the bag design is great, and the backrest feature a definite plus, especially for those, like you, who do have back problems. Anything that will keep someone riding is a good thing. For that, they are more worth the price.
For me, though, they are just too rich in price. I don't need a backrest, just would be nice to have.
Sorry for any misunderstanding.
