Russian Imperial Stout

Since I'm moving out of my place in a 2 months and downsizing, I'm likely only going to brew once more before I leave and spend the rest of the time drinking down my stash (tough job, I know).  Brewing up a Russian Imperial Stout (RIS) has been a long time coming.  I've mainly stuck with brewing ambers, pale ales and IPAs since I started, with the exception of one cream stout.  That cream stout, Keep At It, was pretty bad, the victim of poor fermentation temperature control and over carbonation.  I still have a few bottles left but they're borderline undrinkable.  

With that being said, I wanted to design a rich, full bodied, motoroil-esque, creamy, chocolaty RIS that I can drink over the winter (hah winter in FL) or cellar for a long time.  After a lot of research on what is true to style, modeling it after other RIS that I like (Stone, KtG, Ten Fidy) I've come up with the following:

Recipe: RIS
Brewer: 
Asst Brewer: 
Style: Imperial Stout
TYPE: All Grain
Taste: (30.0) 

Recipe Specifications
--------------------------
Boil Size: 5.70 gal
Post Boil Volume: 5.20 gal
Batch Size (fermenter): 5.00 gal   
Bottling Volume: 5.00 gal
Estimated OG: 1.090 SG
Estimated Color: 57.6 SRM
Estimated IBU: 84.7 IBUs
Brewhouse Efficiency: 65.00 %
Est Mash Efficiency: 65.0 %
Boil Time: 60 Minutes

Ingredients:
------------

8 lbs                   Pale Malt (2 Row) US (2.0 SRM)          
1 lbs                   Black Barley (Briess) (500.0 SRM)       
1 lbs                   Caramel/Crystal Malt -120L (120.0 SRM)  
1 lbs                   Chocolate (Briess) (350.0 SRM)         
1 lbs                   Oats, Golden Naked (Simpsons) (10.0 SRM) 
4 lbs                   Light Dry Extract (8.0 SRM)     
1.00 oz               Magnum [14.00 %] - Boil 60.0 min  
1.00 oz               Warrior [15.00 %] - Boil 60.0 min   
1.0 pkg               California Ale (White Labs #WLP001) 

I had to use some extract because of the constraints of my 7 gallon mash tun. I'll be making a 2L starter, mashing at 154F (subject to change) and fermenting at around 66F.

I think I am going to make 6 gallons of this and sour one gallon. As you can tell from my previous posts, I love souring stuff and this should be a fun experiment. I am also toying around with the idea of adding some bourbon oak cubes or cacao nibs to part or all of the batch. It's going to be a lot of experimentation for sure, but I won't worry about that for a month or two after fermentation is complete.