The % of grist is a bit deceiving since it is an extract w/specialty grains recipe. The .5# in a RP works - that's what I put in mine along with 1# chocolate and it scored over 40 at NHC.
Also at that high a SG, it can stand to have IBUs in the low to mid 50s. I like c.n.'s hop suggestions, but I would maybe bump the starting hops by 1/3 to 1/2 of an ounce.
Kegged: APA, Old Ale, Bock, Robust Porter
Primary: Imperial Milk Stout
Next Up: --
Projects: Brutus Strut-stand (Done), Freezer Conversion (Done), HERMS (Done), Lager Fermentation Mini-fridge Extension (Done)
Drinking: Great Lakes Edmund Fitzgerald, Fuller's 1845, New Glarus Moon Man, Tröegs Troegenator