Hi, I was just about to make a topic on this exact issue as I am looking at optimizing our mash pH (it's currently around 6.2). I tried 5.2 buffer from a chemical supplier but it doesn't seem to do the trick. I even tried it on a small scale, adding 1x dose at a time until I gave up at 10x their recommended dosage and my pH was only 5.5.
I am planning on doing a small scale assessment of citric and hydrochloric acid with our brewing water to see which works better/is more economical. Agporte, I'd love to know what you have concluded/ended up doing. And NEPA and Jeffw, if you use backset, doesn't that turn your whiskey into a sour mash whiskey? I've thought about doing that as well but that may have to be a separate product.