Has anyone used a Thinline Ultra Sheepskin Comfort Half Pad?

I am looking for a new saddle pad for my Appy mare. I have pretty much decided on the Thinline Ultra Sheepskin Comfort Half Pad. It is supposed to mold to your horse's back and alleviate stress on the back, etc. Also, what are shims?

I believe MIEventer is using one and like it. I have the standard Thinline contour pad. Wouldn't ride without one - it's indeed absorbs the shock for both - horse and the rider.

Shims are pieces made of Thinline you can add on front, back or middle of the saddle to get a better fit. Like my horse is asymmetric on front, so I need little extra-padding behind the left shoulder.

I have the Thinline Ultra Sheepskin pad - L-O-V-E IT!

It provides shock absorption while not being overly thick. I've had it on both my wide QH and my narrow TB (with their respective saddles) and both horses seem to like it. I don't worry about it changing the fit of my saddles as much as I do with my fleeceworks or mattes pads.

My pad, however, does not have shims.