I'm making one of these very soon. The recipe I came up with uses midnight wheat for the color. I don't have my exact number off-hand, but the SRM was almost 30 and I believe I'm using .5lbs.
If this grain works out as they say it does (color with zero roast flavor), I'm going to change my Black IPA and Schwarzbier recipes to use it instead of carafa, chocolate, black, etc.
Bottled: Atonement Brown Porter