Like TMX said, so much depends on your system. I have a SS false bottom and pump to recirculate, and found that .032 works well as long as I don't have much huskless grain (rice hulls when I do), but that .030 got me a stuck sparge twice. Like coolman26, I run the huskless grains through first, and I double mill them as well. When I BIAB, I leave the gap alone, and just mill everything twice. I use a feeler gauge to set my gap, and check it on every brew day.