I dont think it would be too much. Black malt, to me, lends an ashen/burned flavor that I try to avoid. I think alot of homebrewers make the mistake of blasting the snot out of their stouts with heavy roast and they just become acrid. I love Roasted Barley and I like to get a touch of Chocolate malt in there as well. I think a touch of it lends a little complexity to the roasted flavors and keeps stouts from becoming one dimensional. My rule of thumb is to keep my roasted malts at or under 10% of my grist bill and then I throw some token Carafa III to really blacken the color with minimal flavor impact. I think if you are making a Dry Stout that you might want to keep the heavy roast flavors down. I always think of Guiness and how it is pretty tame in the roast department.
This is my recipe:
07 lb 00 oz - Simpson's Golden Promise (59.9%)
02 lb 04 oz - Briess Flaked Barley (19.2%)
00 lb 14 oz - Crisp Roasted Barley (7.5%)
00 lb 08 oz - Briess Flaked Oats (4.3%)
00 lb 08 oz - Weyermann Acidulated (4.3%)
00 lb 05 oz - Crisp Chocolate (2.7%)
00 lb 04 oz - Weyermann Carafa III (2.1%)
In hindsight, I would have done a protein rest due to the flaked adjuncts. My fermentation stalled at 1.020 and I think its due to longer chain sugars of those ingredients. It wasnt yeast health, pitch size, or aeration. It also wasn't due to a strain that isnt highly attenuative. I added Brett to take it down to an FG of 1.009. I also mashed at 148 so it wasn't a result of mash temp. Maybe somebody else can tell me otherwise, but the high % of flaked adjuncts seems like the only reason left...
