IMO, the SO4:Cl ratio is of little use. The actual concentrations are far more important. This is especially important in something like an IPA, where very high sulfate levels are preferred. You're much better setting your chloride at a modest level, and adjusting your sulfate to taste. I just add Gypsum to my (fairly soft) well water, and don't bother with a CaCl2 addition in my APAs and IPAs. I shoot for around 250ppm of sulfate, but others prefer it much higher.