I was told one of my mare's needed a flex tree due to some muscle atrophies she developed before me caused by an I'll fitting saddle.she is out right now due to an injury but I went ahead and bought a deb Sibley ultra flex anyway. I bought it used. I rode it today on my other mare. I rode in a fleece lined wool reinsman pad that's about an inch thick and my deb Sibley ultra flex. When I took it off and looked at the sweat patterns she had a strip down her back that was dry and her shoulders were dry. Good or pad? Opinions? I suck at sweat marks. When I ride this particular horse in my treed saddle with my one inch best ever she only has the strip down her back which I was told was okay.