wallet back size advise needed

[Studio-N]

hello my wallet making peeps. I'm thinking of offering embossed wallet backs (some examples shown but would be UNpunched). of course unless you're working from a kit, everyone does theirs a little different in size. So this is kind of a poll. What would be a good size to make the wallet back? Or would it be better to just make it oversized so it can be trimmed to fit? This is generally 3/4 oz leather but that is easy to change. Any help or suggestions is appreciated. cheers!
As a reference, these are kit backs and are 3 1/2 by 9 1/4. Once I lock down the size I'll have a clicker die made for it.

 

[Rockoboy]

I have never made a wallet, so no help here, but when you get up and running, I might be a buyer.