Chocolate Guinness?

Hey guys, im thinking about making a Imperial chocolate oatmeal stout for my second batch. i read that to make a Guinness recipe you can add soured beer to your batch to get close to the real deal.

i want to know if anyone has tried this with a big chocolate oatmeal stout(or similar) and what the results were. i like Guinness and choc/oat stouts but dont know if there is an issue i may be over looking. thought i would get some advice or even a recipe if anyone had success.

CHEERS!

I did a Redhook Double Black clone a while back and it was amazing.
I added some oatmeal to the second batch i did and it was a little thicker and i loved it. I am actually doing it again this weekend if all goes well.
Here is the recipie I used and adjusted to.

https://www.homebrewtalk.com/f12/recipe-redhook-double-black-stout-145663/