What do you mean it "is manufactured to a shape that it is parallel to the binding"? You can rotate the highback, so that it is not parallel/perpendicular (depending on how you look at it) to the binding by loosening the two screws were the highback attached to the baseplate (check the manual).
yeah of course i can rotate it. but then the problem is that it doesnt fit properly with the heel cup after the rotation. it doesnt even sit on the heel cup anymore