Water for Belgian Dubbel

[WiscBrewer]

I'd like to brew the "Black Scapular Dubbel" from "Brewing Classic Styles". I could use some help, though, with the water. I brew with 100% RO and use Bru'nWater. Could someone suggest a good target profile for this beer?

A second related question. I've tried to figure additions based on the Chimay profile but had trouble getting the Sulphate low enough while also getting Calcium high enough, using Gypsum and Calcium Chloride. I got Calcium to around 20ppm, but I've heard that 40 is generally needed. Is that true, or is 20 OK in this case. Many thanks!

 

[55x11]

I'd like to brew the "Black Scapular Dubbel" from "Brewing Classic Styles". I could use some help, though, with the water. I brew with 100% RO and use Bru'nWater. Could someone suggest a good target profile for this beer?

A second related question. I've tried to figure additions based on the Chimay profile but had trouble getting the Sulphate low enough while also getting Calcium high enough, using Gypsum and Calcium Chloride. I got Calcium to around 20ppm, but I've heard that 40 is generally needed. Is that true, or is 20 OK in this case. Many thanks!

I would use Brown balanced or Brown Full. Generally at least 40-50 ppm of Ca is needed for yeast health, flocculation etc.
1.5g of gypsum and CaCl (per 5G RO water) should get you close on Ca, S and Cl.
May want to use baking soda to increase alkalinity, mostly for pH matching (?)