
I'll address your last post before I post what I was going to post last night.
Adding water to a sparge won't change the grain bill at all. It is as efficient (not more, not less) adding the water all at once as it is adding it in stages. So, grain bill stays the same. The L/G ratio refers to the mash so that will change if you do not do a pure, full-volume BIAB.
A for your last sentence, the BIABacus for extract will assume you are adding it at or before flame-out. There's no need for it to do anything else. I might be missing your question here sorry Richard but you wouldn't want to be adding water at flame-out if you could have put it in the kettle before. And, as a matte of interest, if extract is used, the TWN and SWN will go down as there will be less liquor retained by the grain. I've factored that in.
Thanks for looking into the above

Using Section X and Y to Increase Transparency
On my first test of PR1.3Q, I compared a BeerSmith2 file with the BIABacus but this always takes ages and by the time I had finished, I was drunk I think - lol. I'll have another look at that file over the weekend, though. Anyway,it does appear as though 1.3Q is working fine on the extract. Here's how I made checking the numbers a whole lot easier. Open up this file... Here's the critical info...
1. Set Desired VIF in Section B to 5 gallons.
2. Set OG in Section 3 to 1.092/4 (that is 2 x 46.2)
3. Set 5 plus 5 pounds on the left of Section C and you'll see that the left and right side balance.
4. In Section X I have set a whole lot of things to zero including evaporation. This 'brings' all the numbers from boil start on together with no distortions.
5. In Section x I have set the auto-efficiency to 100%
6. In Section Y I have set both fermentables at 100 and 0
Basically in this 'brew' we are putting in 462 US sugar points (10 pounds x 46.2). Divide that by 5 gallons and you get 92.4. In other words, we can expect an OG og 1.092/4. Half the bill is extract and so we have a GIB of half of 92.4, i.e. 1.046/2.
And if you get rid of that b in Section C, then you'll see the GIB jump to 1.092/4 which seeing as we have zero evaporation is correct. So, all is good!!!!
I think the above is a good example of how quickly (it took far more time to write this than the minute or two setting up the above) the BIAbacus can be used to check it's own calculations as well as those from other sources.
Auto-Kettle Efficiency Also Works Nicely with the Extract.
Not sure if you noticed the following but do this in the file above...
Delete the 100 on the first line of Section X. Notice your EIB is now 81.3%? Now get rid of the b beside the second fermentable. Notice how the EIB drops down to 61.6%? This is another major plus of The BIABacus. It will actually auto-adjust for the myriad of situations that putting sugars or extracts into an 'all-grain' beer can result in.
Very Advanced Stuff
When working on the formulas for this, it made me realise something I've never seen written anywhere else before. In a grain brew that has extract or sugar, there is an immediate integrity loss. (mally, this relates in a way to a weight versus sugar contribution question you had here ages ago. You were coming from a different angle then, I think, but it is relevant here.)
In real life, especially for those using a BIABacus recipe from another BIAB'er, this isn't anything to worry about really but it is interesting to see it never talked about.
Let's use the file above as an example. Let's imagine that was in a book and the recipe was 50$ by weight grain and 50% pure sugar. If you were a three vessel brewer and had very poor EIB compared to mine, then this means that my brew will actually have more sugar contribution from the grain than the original brew.
As I said, in real life, this isn't really going to be anything to worry too much about. It's something though that the advance brewer might take into account in extreme situations. As for 'fixing' the problem, well you really can't unless you are given the weights (not percentages) of fermentables from the original recipe and the original brewer's EIB.

PP