Assuming your saddle fits properly you do not need a thick or sheepskin half pad of any sort. It will just affect the fit negatively. If you feel that you need something go for the thinline as the thinness won't adversely affect your saddle fit.
I received my thinline ultra contour pad in the mail yesterday and it doesn't appear to affect the fit of my saddle (it is crazy thin) but wow! I had no idea a pad could make such a difference! Things just feel more connected and less, well, likely to bounce. Anything that improves my horse's comfort and mine as a plus is good in my book!
I apologize for not responding sooner- my horses got moved to a MY NEW BARN this weekend, and although it was very exciting, I was very busy. Thank you everyone for responding, and I have definitely narrowed down my list and learned a lot!!
I have a thinline ultra for sale if you are interested
Only reason I am selling is because I got the thinline sheepskin pad. I LOVE thinline pads and my saddle fitter swears by them as well.
This is the one I am selling. They are $94 new. I can get a pic of it next time I am at the barn if you're interested. I can't get over the difference thinline has made in my girl. I swear by them now.