I'm planning to brew an oatmeal stout and read that Gordon Strong recommends keeping the dark grains separate and adding after mashing out or steeping prior to mash. Reasoning is to avoid prolonged heating which increases harshness/astringency. My source water is good but just barely into the "moderate" range of alkalinity and my mash pH would be around 5.4 if I were to mash with the dark grains. If not, mash pH would be considerably higher. The question for me is whether or not risking more harshness/astringency is worth a better mash pH. I'd like a nice, non-cloying sweetness with my oatmeal stout. Would it be advisable to use lactic acid to get a good mash pH (and add the dark grains after mashing) or would that push the wort into the realm of being too acidic? Any opinions?