BIAB with a mash out

I've been using http://www.simplebiabcalculator.com for calculating my temps for infusion and the mash out.  However, I've set up a mash profile (single step infusion) to try and mimic this for BIAB, however, my water volumes tend to be off of the brewsmith calculation.  Just as an FYI, for my mash out, I add boiling water to my existing mash to raise the temp to 170.  Are there any other BIAB brewers that use this type of method and have reflected this in beer smith 2?  Any thoughts on how to reflect this in the mash profile? Thanks!