Hey there, thought I'd add onto this. Late addition I know, but it might clear some things up with regards to Philly Sour. I just produced my first sour, I was aiming to hit close to Colonial Brewing's South West Sour. I think I got pretty damn close. I'll share my grain bill and mash steps from Beersmith below and then explain what I did to sour, my goal, is to do a kettle sour eventually, but this one was nice and quick for a first time sour.
Grain bill - 23L batch:
Ignore the Lactobacillus, thats in there for when kettle souring.
Mash Steps:
I know this may be a high temp to mash at, I didn't want much more than 3.5-4% alc, I was looking for something sessionable. Change as you like.
Ferment:
I added 1 packet of Philly Sour, this was borderline the right amount according to the packet when it comes to grams per volume. As it turns out, it worked really well. I left this sit for 3 days to let Philly work it's sour magic. I then pitched 1 packet of US-05 and left it until 10 days.
Kegged it up, left for 1 week and tested it. After 1 week in the keg, gassed up and cooled to very cold, I loved it, decent sourness, I didn't test the PH so I don't know, but I will get a PH meter and test when I stop being lazy, I still have 10L left.
It's now been 2 months since I made this batch and I just gassed some up this week, I think it has actually mellowed a bit sourness wise. Still, I think it kicks ass.
Temp wise, I fermented this during winter in Perth Western Australia, so my room temp was around 18-20deg Celsius majority of the time, a bit warmer at night if I lit the fire.
Hope someone finds this useful.
Cheers