First Imperial Stout: 2 questions

1)  If I use distilled water, what combination of salts will provide adequate RA without resulting in too much Ca++, Na+, or Mg++ ?

2)  Should I consider using debittered rather than standard black malt since the style calls for large amounts of dark roasted malts?

…  I will be brewing a 5 gallon all grain batch.

  1. Post your recipe
  2. Have you downloaded the Bru’n water spreadsheet and read all the included info?  Also look up kaiser brew website
  3. Post your recipe

Thank you for the advice. 
I will post the recipe when I’ve made a final decision which to brew.  I’ve found a few to choose from but have brewed a witbier recipe from an unknown source and had a final product with too much spice in the flavor profile, so I’m reluctant as to which recipe to use, depending on where I found it.
I’m pretty green regarding the Imperial Stouts.  I plan to use oatmeal and saw a recipe posted in this forum recently that appeals to me but I plan to run it through a recipe program for further evaluation:

Imperial Oatmeal Stout  (5.5 gal)

0.25 lb Rice Hulls (0.0 SRM) Adjunct 1.47 %
11.20 lb Pale Malt (2 Row) US (2.0 SRM) Grain 66.08 %
2.00 lb Barley, Flaked (1.7 SRM) Grain 11.80 %
1.00 lb Oats, Flaked (1.0 SRM) Grain 5.90 %
1.00 lb Roasted Barley (300.0 SRM) Grain 5.90 %
1.00 lb Special Roast (50.0 SRM) Grain 5.90 %
0.50 lb Chocolate Malt (350.0 SRM) Grain 2.95 %

3.28 oz Styrian Goldings [5.40 %] (60 min) Hops 53.9 IBU
1.50 oz Chinook [13.00 %] (10 min) Hops 21.5 IBU

0.11 tsp Fermcap -use 2-3 drops (Boil 60.0 min) Misc 
1.10 tbsp PH 5.2 Stabilizer (Mash 60.0 min) Misc 
1.10 items Whirlfloc Tablet (Boil 15.0 min) Misc 
1.10 tsp Yeast Nutrient (Primary 3.0 days) Misc

1 Pkgs SafBrew - US 05 (Fermentis)

OG 1.082
FG 1.018
ABV 8.38%

That recipe doesn’t look like you’d need to swap in any dehusked roasted grain.  You could add half a pound of it to get closer to 10% roasted grain.

Two additional comments: 1. I’m not sure a big late addition of Chinook would be my go-to for this style.  2. Most RIS’s include some darker crystal malt which helps to temper the roast and make it seem more like chocolate, less acrid.  I don’t have a lot of experience with Special Roast but I don’t remember it being all that sweet.

This recipe looks like it may be more traditional for a RIS (except for the oatmeal) ?

5 gallon batch

16 lb    American Pale Malt (2 row)
1 lb      Crystal Malt 90L
1 lb      Crystal Malt 30L
1 lb      Quick Oatmeal
1 lb      Rice Hulls
0.5 lb  British Brown Malt
0.5 lb  British Chocolate Malt
0.25 lb American Black Barley
3oz      Cluster hop pellets @ 60 mins
0.75oz  Centennial hop pellets @ 60 mins
1oz      Northern Brewer hop pellets @ 2 mins

Mash 60 mins 154 F
Boil: 90 mins

yeast: WPL051 liquid yeast (do a 1 liter starter)
ferment temp: 66 F

I like to use Special B in my RIS.  Gives a nice raisin, stone fruit complexity to pair off the dark roasted grains. Crystal 120L or 150L would work as well.