Guinness-esque Stout Recipe attempt

In my search for a good Guinness-clone recipe for brewday tomorrow, I came across a number of recipes that looked interesting. I ended up synthesizing them into the recipe below, and would love some critiques or adjustments! I ended up tweaking it in order to get the OG/FG/ABV numbers closer to the actual numbers for Guinness, and adjusted the IBUs to get closer to the 40 IBU figure I've seen for Guinness (but different calculators seem to give IBUs between 35 and 50 for this recipe, so I don't know exactly where it ends up...). It will be done as a 10gal batch, and I may do the souring technique for 5 gallons of that.

Any thoughts from my learned friends?

Recipe Overview
Volume Of Finished Beer: 5.02 US gals
Expected Pre-Boil Gravity: 1.039 SG
Expected OG: 1.042 SG
Expected FG: 1.009 SG
Apparent Attenuation: 78.6 %
Expected ABV: 4.4 %
Expected ABW: 3.5 %
Expected IBU (using Tinseth): 34.6 IBU
Expected Color (using Morey): 27.3 SRM

BU:GU ratio: 0.82
Mash Efficiency: 81.0 %
Boil Duration: 60.0 mins
Fermentation Temperature: 64 degF


Fermentables
Ingredient Amount %
MB - Maris Otter 5lb 10oz 65.7 %
MB - Flaked Barley 2lb 2oz 24.8 %
MB - Black Roasted Barley Malt 13.00 oz 9.5 %

Hops
Variety Alpha Amount IBU Form When
UK Golding 5.0 % 2.20 oz 34.6 Bagged Pellet Hops All Of Boil

I would suggest upping the percentage of roasted and dropping the percentage of flaked, perhaps a full pound of roasted and 1.25 # of flaked. Pale, flaked and roasted ratios for Guinness style seem to be either 80:10:10 which is what I have used and some are 70:20:10. Information I've seen over the years along with anecdotal evidence puts the IBUs at ~36.

Awesome - thanks! I opted for the 70/20/10, and added some rice hulls to avoid a stuck sparge. Will let everyone know how it turns out... Mmmm

I do 2lbs flaked and 1lbs of roasted in my stout and have brewed it many times. I vary the base malt and hops a bit depending on what I'm experimenting with.