I've started making these exotic skinned (mainly reptile) dress belts, and a few of the same in wallets. The stitching will basically go through 4oz of veg tan/latigo and then the skin (3oz for the croc would be the thickest). An 18 needle with #69 thread is what I've been using so far on an old Brother (without walking foot). I'm learning the hard way that a walking foot system is a must as the skins get softer and stickier. I've got no plans for anything other than these types of belts/wallets, so I'm not looking to handle thick amounts of leather. I've been working with leather for less than a month now, but am having a blast thanks to the incredible resources on this site.