My saddler came out recently to look at my Ideal saddle, which I'd asked for a new tree in, and I asked him to put my Wintec on to check it would be ok to use while the Ideal was having a new tree. He said initially it would "do" for a couple of weeks, then picked it up and looked at the back of the cantle, and said "well, it would have been if it hadn't had Cair in it, why on earth did you buy one with Cair?"
Said something along the lines of....where the Cair panels meet it creates a ridge, wihch then rubs along the horses' back, hence so many horses having bad backs after being ridden in Cair saddles. Used it a couple of times while the Ideal was away (horse was just coming back into work after an op so doing mostly in hand and lunging anyway) but must say he didn't go well in it after being back in the Ideal for a while.