I agree with bottlebomber. Have you adjusted your efficiency? I know that's not my problem (would that it were and the problem could be solved!) since my pre-boil gravity is correct. There's got to be something screwy with the beersmith water volume calculations as far as I can tell. I've also posted to that forum and am still awaiting a response. I'll definitely update here if I get any news.
I'm still trying to wrap my head around the information in this thread. But I brewed yesterday and had the same result. Using your format from pg 1 klnosaj:
------------------estimated -------measured
pre-boil SG---------1.056------------1.055
pre-boil H2O vol----7.0 gal-----------7.0 gal
post boil SG--------1.067------------1.060
post-boil H2O vol---5.98 gal----------~5.85 gal
I don't think adjusting my efficiency is the answer because if I do it drops all my gravity readings and pre-boil is always within a point.
Perhaps I'm not measuring my post-boil volume correctly, or accurately enough? I'm a little less that 5.5 into the carboy. I took the 1/2 cup sample too.
What is the most accurate way to measure trub? Trub volume must be completely different depending on hop amounts and whole vs pellet.
Did you ever get a response from Beersmith forums?