Dublin isn't really known for producing RIS.
In my experience with salt additions, trying to match any of the heavily mineralized waters always ends up tasting bad. For some reason, "making" Dublin water doesn't taste the same as using
Dublin water (insert Liffey joke here
), maybe because the reports are wrong, the breweries treat their water, I don't know, there could be several reasons and I'm not a water chemistry expert. But "short of calcium" and needing to up the pH is all the more reason to use pickling lime and leave the baking soda in the cabinet. That's me though, you can do what you like.