Thanks a bunch! I'll be making a sour worted plum saison (plums added at the end of saison yeast ferment), so souring the full volume wort, followed by boiling the wort as normal. Yes, I'd already planned to run off the mash/ sparge into my kettle and boil for 5 minutes before chilling to 92F and pitching the starter.
So I'll just target mash pH of 5.2 and call it good. That makes more sense now too. I plan to sour the full volume wort for ~1.5 days, or until I hit 3.6 pH, and then do the boil.