I do ride western, and I am pretty green, but even my girlfriends who are very experienced were haveing the same problem on her too. So even while I am learning and she is learning and leaning down, are they ok to use, It may be me. I do have a breast collar to I can use, maybe that will help.
With my other guys I never had this problem, but that is back when I rode consistantly. So I guess the combination of fat and green a slip pad will work for now, then evaluate it after the fat and green factors are gone