For those looking to make a leather strap, the leather thickness is normally "sized" and sold based on the "ounce", with one ounce roughly equivalent to 1/64th of an inch or 0.4 mm. So a single leather strip strap should use 5 oz leather. If you are going to fold , cement and stitch, I would recommend 2 oz, as the cement (like Barge) will add a little thickness. Also the location on the hide where the leather comes from can be important if you have the choice. Leather from from the belly can stretch (I can testify this phenomenon is not limited to bovines). Leather from the back is firmer and thicker and probably heavier than 5 oz. Also the weight is just an average - as a natural product the thickness WILL NOT be constant across a piece of leather. A professional can take a heavier leather and skive it to the correct and consistant thickness. The most critical thickness will be the ends (approximately the last 70 mm on each end) which must pass through the panel side slots. This will reduce the effort of skiving the entire length, and allow the center of the strap to be thicker if desired. Also note only the ends could be narrowed to the critical 19 mm width and the center of the strap set to fit your own requirements.
EDIT: Also consider the recess of the side panel if you make your ends wider than 19 mm. They can taper wider in this recess and beyond ~ 105 mm from each end can be as wide as you wish.
… I have a digital 
