Questoins About Leather Thickness

[Buddytink]

I'm trying to make some horse tack and right now I have some 9/10z leather ordered and Im waiting for it to get here. Well I got wondering, If I want to make say a bridle, breast collar, or bronc nose halter and I want it to be inlayed or filigree, Do I still use the 9/10 oz leather, or do I use the 9/10oz leather for the part that will be tooled and then a really thin part for the back, or is both peices of leather (back and the front peice that is tooled) suppose to be the same thickness, just thinner, like both peices 4/5 oz?? Hope that makes since.