It's about time to get this year's xmas beer test batch brewed. I am thinking of brewing a double black ale based on my schwarzbier recipe.
Right now my plan is to use the exact same grain bill but decrease the batch size to hit an OG around 1.080. Also I will increase the hop additions to match the IBU:OG of the normal beer. I will probably mash lower and longer than usual in order to encourage attenuation and am considering a small amount of sugar.
two things leap out at me. first, I don't think you need the sugar at 1.080. mash long and low and pitch plenty of yeast into well aearated wort and it'll dry out just fine.
Second, I would consider scaleing down your specialty malts with the batch size so as not go get too roasty/munichy. when I'm 'imperializing' a recipe I bump the base malt and/or sugar to get my target gravity and leave everything else alone.