Please, feedback on my Russian Imperial Stout: Babushka's Breakfast

What does everyone think of this recipe I want to brew tomorrow? My goal is something more mellow and less harsh than some american RIS's. I am using all UK hops, maris otter base, and US-04 yeast, to obtain a more british profile. Very similar to JZ's "Czar's Revenge" Please let me know what you guys think.

Recipe: Babushka's Breakfast
Style: 13F-Stout-Imperial Stout

Recipe Overview

Wort Volume Before Boil: 7.00 US gals
Wort Volume After Boil: 6.00 US gals
Volume Transferred: 6.00 US gals
Water Added: 0.00 US gals
Volume At Pitching: 5.50 US gals
Final Batch Volume: 5.00 US gals
Expected Pre-Boil Gravity: 1.083 SG
Expected OG: 1.097 SG
Expected FG: 1.028 SG
Expected ABV: 9.4 %
Expected ABW: 7.2 %
Expected IBU (using Rager): 78.7
Expected Color: 48.4 SRM
Apparent Attenuation: 69.7 %
Mash Efficiency: 70.0 %
Boil Duration: 90.0 mins
Fermentation Temperature: 67 degF

Fermentables
UK Pale Ale Malt 18.00 lb (78.3 %) In Mash/Steeped
US Roasted Barley 1.50 lb (6.5 %) In Mash/Steeped
Belgian Special B 1.00 lb (4.3 %) In Mash/Steeped
US Flaked Oats 1.00 lb (4.3 %) In Mash/Steeped
US Chocolate Malt 0.50 lb (2.2 %) In Mash/Steeped
UK Pale Chocolate Malt 0.50 lb (2.2 %) In Mash/Steeped
German CaraMunich III 0.50 lb (2.2 %) In Mash/Steeped

Hops
US Horizon (13.0 % alpha) 1.50 oz Loose Pellet Hops used 60 Min From End
UK Golding (5.0 % alpha) 2.00 oz Loose Pellet Hops used 10 Min From End
UK Golding (5.0 % alpha) 2.00 oz Loose Pellet Hops used At turn off

Other Ingredients

Yeast: DCL S-04-SafAle

Mash Schedule
Mash Type: Full Mash
Schedule Name:Single Step Infusion (68C/154F)
Step: Rest at 154 degF for 60 mins

Recipe Notes

It looks good. I think you're going to get a lot of robust characteristics using special b and caramunich III. I'm not sure that i would have a recipe with chocolate AND pale chocolate in it though.

So I'm going to cut the pale chocolate. On another point I am concerned that it might be overly hoppy. I really want to make a well balanced RIS. At 79 IBUs, i hope it won't be excessively bitter. I want something really smooth and yummy. If I cut the first hop addition even back to 1.25oz instead of 1.5oz, that would drop the IBUs to 67, which might be more manageable. Thoughts?

You will want this beer to sit for a while. With that said, aging beers lose bitterness over time. Depending on when you plan on drinking this, and whether or not you want a more malty or balanced RIS, you may want to actually increase the bitterness. I'm sure someone around here can give you better numbers, but I think you can expect to lose about 5-10% of the apparent bitterness of a beer per year. Unless you ferment this pretty cool (~60*F), the beer will probably be too hot for no less than six months. Unfortunately that means you'll lose most of the flavor and aroma qualities from the Goldings.

Personally, I would up the roasted barley to 2lb or more and the chocolate to at least 1lb. These beers are ridiculously roasty. I think that you may end up a little unsatisfied if the beer doesn't have enough roasted quality. Additionally, I would aim for an IBU:OG ratio of 1. That way, in three years, you can open one of these and show off your slightly malty, well aged lovely gems.

That's my two cents.