Calculating for extra material needed on template

[ffjdh]

I am working on a dropout scabbard for an axe, something like this:http://dalesiogrp.com/wp-content/uploads/2016/01/DropOutSwivelAxeScabbard6lb.jpg

I am making a template with a manila folder.  Is there a general guide or a way to calculate how much extra wiggle room I should include on my template to account for extra leather need to account for the bends bending made in the leather?  The leather I’m using is around 12oz

Edited June 14, 2022 by ffjdh

[JollyDodgerCanvas]

Making prototypes is how you discover your design is affected by material choice. Find a material, cheaper, with similar thickness and make a prototype and measure the error. I use layers of cheap upholstery vinyl glued together or rubber to simulate thick materials, heavy canvas could do as well.

[PastorBob]

When I am making holsters that fold over, I generally add half the thickness of the firearm, plus the thickness of the leather, then add for my stitching line (normally 1/4" gives me enough room for the stitch line plus a little extra so I can sand down the edges if there are any imperfections)....I should say when there are imperfections.