Obviously, there are a lot of different variations for Porter. I like the robust version as opposed to brown Porter as I am not really fond of the flavor character imparted by brown malt.
I use a bit of black patent in mine and chocolate malt (sometimes chocolate rye).
You can predict the mash pH with BeerSmith or more accurately with Bru'n Water if you know the mineral content of your water source or if you use RO water. If the predicted pH looks too low, you can keep some or all of the dark grains out and add them at mash out since they have no fermentables in them. I do that with my R.I.S. and it works well. Just stir them in at mash out and vorlauf until the color is right
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