I am kind of late to the party :) but if you need any more info, pls feel free to message me. I have been a dealer for 5 Star (& other brands) for many years but the 5 Star outsells any of the others 100 to 1 at least.
I know the website "suggests" the 7/8 for the general use, but with the 5 Star pads having the highest compression/concussion rating, you do not lose that when you go thinner. When you think about it, the 7/8 is only 1/8" thicker than the 3/4 - not much comparison! What we are finding more now a days, that you want to find a a pad that compliments the fit of your saddle. If you have a good fitting saddle, you don't want to go w/a thick pad - that can cause a too tight fit & potential pressure/sore areas. I personally own 1/2" & 3/4" - & with my mares & saddles, only use my 1/2". These pads do not "squish" down like many pads either. Also, it's hard to tell on the thickness - they are "rated" at the felting factory & it's usually done by weight. If they felt them more/harder, a 3/4" might be thinner than another 3/4" that they didn't. (I hope that made sense.) And it's almost impossible to tell thickness by measuring any wool pad's edges - due to the wool will "fluff".
Just my 2 cents worth! :)