I just bought a new Big Horn Ralide®Flexible Saddle #299 with full QH bars. It is my first synthetic. I love the feel of the saddle, super comfy but it is slipping side to side quite a bit. I am using a neoprene girth and a tacky too pad. I had my horse with me when I bought it and the fit seems to be good. Any thoughts on why it is slipping and how to prevent it? Thanks!