Ok to half 2-part recipe or dilute it?

I have been dosing two-part with a dosing pump in my red sea max. I was using Kalkwasser and could not keep up with the calcium and alkalinity with fully saturated kalkwasser. I was able to keep the top off full in the sump with the kalkwasser. Because the two-part is super concentrated, I am not able to keep up with the evaporation. Does anyone know if you can just half the recipe in the same gallon of water and if so, is halfing the mag part just that easy, cutting it in half as well? If I were able to get double what I am in dosing in liquid I wouldn't have to top off, you dig?