Length difference back and front of wallets?

[CJW306]

If I was making something similar to this holder with 3-4oz leather, does anyone know what sort of length difference would be required between front and back? I assume that the back needs to be longer than the front, but I wonder if there is an aprox length difference for a rule of thumb or calculation based on leather thickness?

 

Thanks

[treyman]

My back is 9" and inner is 8.5" 

[NVLeatherWorx]

Half inch is as big a difference as you want to go; I do mine at 3/8" difference (which to me is the opposite end of the equation, no closer).

[MudBugWill]

I add half an inch for the back as well.

[dfrensdorff]

1/2" for mine as well

[CJW306]

Thanks for the replies, very useful