Saddled slipping back- How to stop it!?

[AABBCC]

As the title says, my saddle pad always seems to disappear backwards during every ride! We've had the saddle looked at and it was deemed a good fit so I don't think it's that...
Anyone got any ideas of how to stop it? I'm thinking of getting one of those gel pad things but not sure about it because I don't want to affect the fit of my saddle...
Also, I ride in a saddle pad and then a riser pad (riser pad doesn't seem to slip) so I'm not 100% sure which "layer" I'd put the gell pad on for maximum effect?
Any advice is greatly appreciated

 

[abbijay]

If it's just the saddlecloth/numnah that is moving just buy a different one with straps that fix back to the girth straps. I like the Nuumed ones but they're not the cheapest.
You say your saddle is a good fit but you use a rider pad? Was it checked by a qualified saddler and is the riser a temporary measure or intended as a long term solution?

 

[Bombaybuddy]

Try a breastplate?? I had excactly same issue only in summer when my gelding would put on weight.
I swear by my breastplate or a shires non slip saddle pad they are both great!

 

[sbloom]

It's usually a sign that the saddle is trying to move forwards, instead the pad moves back under it. Check the saddle is back, the front edge of the tree points should be 2 inches or so behind the back edge of the shoulder blade. If all really IS well, then a firmer pad with good fixings is a better solution than anything grippy. I always say that a cotton pad should almost stand up by itself.