I've found that my (thin skinned) gelding is more prone to get a sore
back when I'm walking a lot then when working at a faster pace. I ride
him in an ortho-flex (with thin-line pad cut out from the back few inches
of the panes to raise them off his loins) This set-up has no pressure
points but he would still get sore - I finally decided the cause in his
case was friction (he has a nice long stride and his loins are working
when he walks.) I finally found a gel pad big enough to cover the
ortho-flex panels and have not had a sore back since then. I really
love the gel pads, they will even out a slight pressure point problem
too.
Best of luck,
Teresa and Grey Moun (thank goodness you finally figured out how to stop
hurting my back)