Tim at CBS told me to use Beersmith's BIAB mash profile, which should provide a full volume mash. When I tried that, the agreement between Beersmith and the CBS water spreadsheet was pretty good. It became spot on it I edited Beersmith's BIAB residual water value, under the advanced settings, to match the value in the CBS spreadsheet. (In fact Tim said BS is the way to go, and to ignore their sheet if you have it.)
By default BS uses a grain absorption value around 0.58, I think... CBS uses different units in their spreadsheet but in BS fl oz/oz it came out to 0.8 if I did the math correctly.
And as jrodmfish noted, CBS has an equipment profile for download too. It includes the specific heat and weight values for the basket and so we should be able to have BS calculate strike temperature.
I don't have my Nano Home 20 yet but this seems like it should all work.
It's going to be a long couple of weeks til it gets here.