saddle slipping woes

[Sally Spangler <stepnout@swva.net>]

Now that the Blue Ridge finally has some sweat-weather, I can't get my
Desoto saddle to stay put on Misty on steep grades. (A month ago in 50-60
degrees, we were trotting down several miles of mountain sans problem.)
(This is a 14h, slender, short-backed mare with fairly level withers.) It
rides up onto her shoulders (whereupon she begins stumbling) or occasionally
back toward her rump. Currently using a Woolback pad, which has been
great--no heat bumps or dry spots as with a felt pad.  I'm using a crupper
(have tightened it seriously each time, am concerned about her tail now!)
and a breast collar (also pretty tight.) The thick fleece girth is as tight
as I can get it without causing discomfort; switched to it when she got
serious welts after using a string girth.  The girth, moreover, does not
appear to be slipping forward or back, and the saddle doesn't slip sideways.  

Suggestions to date:  get a thinner pad, use a breeching, change girths,
maybe velcro to the hide!  I have not had a chance to check out many other
saddle pad styles to date, and that's my first inclination.  Next chance I
have to attend a ride I'm planning to peruse the stuff everyone else is
using...want to see before buying, trying, failing again.  Meanwhile, anyone
want to comment or elaborate?  (I'll THINK of joining AERC when we have
accomplished certain basic procedures, such as keeping the tack and rider in
place for at least 25 mountain miles at speeds faster than a walk...)

Thanks,

Sally Spangler (stepnout@swva.net)