Bring the mash pH up another point. I target 5.5-5.6 mash pH for stouts and porters and it makes a world of difference.
can you expound?
I always had an issue with the roast character on my darker beers that I couldn't quite put my finger on. The roast character seemed a bit muddy. Once I started targeting a higher pH the roast notes really started to pop out a bit more. The roast wasn't harsher, but it did jump out a bit more.
A good example is actually the counterexample. In a dry Irish stout like Guinness the roast character is exceptionally smooth, and the pH happens to be on the lower side. That's no coincidence - the acidity tends to mute the roast character. Another example is coffee. For a medium-roast coffee a touch of acidity is nice and adds a bit of brightness. But for a dark roast or espresso, excessive acidity really clashes with the roast.
You can always play around with this post-fermentation by dosing with some baking soda if you don't want to invest a whole batch. But targeting a higher pH was a one-step fix for mediocre stouts and porters for me. It makes a surprising difference in the finished product.