I'm surprised CW hasn't chimed in on this yet. Don't do it! Especially to a 10 year old runt they increase felt recoil and can collapse with heavy recoil. Buy a youth pallet wood stock and if you still need something shorter cut it down and put a slip on limb saver recoil pad on it. make his shooting experience and his first deer hunt a positive thing.
I'm here!! Just reading this now...
I have three words for you...
DON'T DO IT!!! The stocks construction is SUB standard and WILL collapse under even moderate recoil. (20 Ga can recoil pretty good esp with slugs!) If a scope is used, there is a real danger of EYE REMOVAL!!! One member here had some bad scaring and almost did loose an eye form these wretched things. Personally I won't own one. But if I did I would limit the use to a RF/22H/223. Its simply not worth the risk!
Get a youth stock or cut down a pallet wood stock for him! PM me if you need one, I think I have a couple..
CW