Thanks Denny and bluesman! I have a pH meter and am pretty anal about checking my runoff pH.
I have another question that came up after I punched everything into Beersmith. I was basing my recipe on Tom O's partigyle calculator, and Kai's partigyle mash thickness table. If you don't have it in front of you, it assumes a 60/40 split of the grains' gravity and color contribution and 3.5L/kg to hit my target first running gravity and volume. The issue is, my mash tun is not nearly big enough to hold all the grain and water at the required thickness.
Should I try to figure out all the gravities from a first, second and third runnings, or should I just do it on-the-fly on brewday? On my sub-recipes for the individual beers I have pre-boil gravities and volumes. Would I be able to just measure my volume and gravity as I mix the 3 runnings to get to where I want to be?
The confusing thing to me is that my "master" recipe with all the grain as one recipe gives me a pre-boil volume of 52L, but each sub-recipe gives me a pre-boil volume of 31L, so I would actually need 11L more than Beersmith tells me. Is this something to do with the way Beersmith calculates boil-off?
I'm not super particular about hitting my numbers exactly, but to be off by 11L seems like a lot.
EDIT: I think I figured out the volume issue. I found a set volume for "lost to trub and chiller" of 3.79, so it was double counting that volume, and also it had a set boil-off volume. When I fixed both of those the numbers matched up.