dunno of this is helpful to you, but, I've read that one should keep their back straight. when I ride by shop windows I can see that mine is not. I've also read, it helps to straighten your back by visualizing pushing your butt out, as if, to arch your back the other way. which of course, I can not do, but I can visualize that. sometimes I have to remind myself. it feels a little awkward, but I've done it riding by a shop window & my back is better but still not straight & my butt certainly is not sticking out. but if is a step in the right direction