I don’t have those programming skills, but I went about the problem of maxi-BIAB calculations a different way, and came up with a solution that works for me.
I have a 16 gallon Bayou Classic pot and I like to make 10 gallon batches, my grain bill for my double IPA’s is usually around 27lbs (half a sack MO usually). I could get a bigger pot I suppose, but I brew in the kitchen and I don’t think that would be fair to the ceramic cooktop. I’m surprised it hasn’t broken, as it is, with the weight.
In order to get two Corny Kegs of beer, I usually have to do a small sparge of 2 gallons. That could be a “dunk sparge”, but in my case, I gave up “pulling the bag” as it makes a bloody mess in the kitchen, and instead I drain the wort from the ball valve through a silicone tube into another pot. I heat the 2 gallons of sparge water in a saucepan to mash-out temperature and pour that on top of the mash after it has drained, or as it is draining. I am fairly sure I haven’t noticed any significant loss of efficiency doing that vs a true full volume mash.
It all comes together in a brew sheet that I wrote (I used KompoZer, a free HTML editor program you can download). The brewsheet pulls information from the recipe. I let BeerSmith work out everything as though it was a true full volume mash and most of it follows through into the brewsheet automatically as usual. The total water needed appears in the new brewsheet. The only thing I don’t let go through is the strike water temperature and mash details. Instead I work this out manually using the infusion tool in BS and record it in the notes section of the recipe. $NOTES then pulls that information from the recipe and puts it in the BrewSheet…..In the attached brewsheet the text “This is a Maxi BIAB: Heat TWN minus 2 gallons (used later for sparging) in BIAB pot to 161.5F. Initial steep temp 152F. Steep time 90 mins.” Is recorded in the notes section of the recipe and appears in the brewsheet automatically.
It’s a half-assed solution but it works for me.
I am attaching a pdf of an actual sheet. I tried to attach the html brewsheet but the attachement was disallowed as was identified as a possible attack vector. I will email it to Jimmy to se if he can put it in. If he can feel free to load it into your BS or modify it.
I really recommend making your own brewsheet, at the very least you can get it to fit on one page. It’s nice to have what you need on there too, and take out REALLY unnecessary instructions like “drink and enjoy”

Does anyone have any useful BeerSmith modifications up their sleeve?
Right click > "Save link as" for html brewsheet