Hope this isn't a repeat, but I answered yesterdy and don't see it anywhere on ridecamp so am sending again :)
Subject: re:saddle pad slip
Chris, if it's the HAF pad with the wool underneath, then you can't fix it even if you tie it on. I had exactly the same problem. I've used HAF pads with the waffle pattern for several years and thought it would be nicer for the horse the have the wool...wrong! I went back to the waffle ones. If you want a really nice pad with the wool, I also bought a Christ pad from Teddy at Running Bear and it is fantastic and does not slip at all. Must be a different kind of wool and different cut. Cindy