I take you through my non-slip history.
Joy is a somewhat round sec d. What was happening with her was that the saddle was shifting forward onto her big shoulder. The best thing that helped was for her to lose her excess weight (but she's fat again now).
In the meantime I found the best non-pad was the Stephens gel-eez which I would use with my usual numnahs. It was fab. It could get dunked in a trough after each ride and when it started to lose stickiness then I'd wash it in the sink with washing up liquid.
However, what I hadn't considered initially but worked wonders when I did get advised to try it was a humane girth. I have to admit I was very anti them but she's much happier in it and the saddle doesn't get pulled forwards now, even without the pad. I'm converted as they are right for us. You can get a shaped one that is even better.
In fact I went from an elasticated girth (both ends) and forgot to check the girth after getting on the first time I used the humane. I got back to the yard after a very fast demanding hack to test it out only to the girth hanging down under her belly in throat lash styley but the saddle hadn't shifted. This proved to me that a) it was the girth that was the issue, and b) my position can't be that bad considering I never even noticed! :redface: