I also used to use a CARX + kalk reactor but abandoned them years ago for the Balling Lite method.
I do have a brand new deltec kalk reactor here though if you want one
I mix
2kg Ca into a 2.5g fish tank.
2kg Mg into a 2.5g fish tank.
1kg Ca into a 5g fish tank.
This is below the max saturation point.
I just dose straight MgCl to keep the sulfate levels lower. I stopped dosing magnesium sulphate years ago.
I have never found that dosing the Balling Lite method has any effect on lowering my salinity when mixing at this concentration.
I find that the Mg consumption on the system varies the most depending on what salt brand you use.
When I used RC, i had to dose a fair amount of Mg, and I too always found that I was having to adjust my Mg dosages as they seemed to change a fair amount.
When I used Royal Nature and DnD I didnt dose ANY mg almost at all.... ever.
It was to the point where I was convinced something was wrong, lol.
When I used TMC I had to dose some Mg.
Currently I am using the Fritz salt as its giving me great results at a budget price and I find my Mg consumption to be just a tiny bit higher than when using TMC, but this could be related to coral load currently as the diff is so small.
And I should also mention that we test every day so parameters stay VERY stable.
And again, no matter what salt i used, what the bioload was, how much we dosed, I never saw any effect on salinity.