I use the temp expansion (4 %) for my post boil volume, but set the expansion value to zero (0%) to figure out my pre-boil volume. I also know my boil off, trub loss, and the volume I want into the fermenter. In doing so, I have been able to accurately create a set of measuring sticks that I use to fill my kettle when sparging, and to also check that I have boiled down to the level I want prior to cooling and moving to a fermenter.
The way that I figure it is that if I can keep my volumes consistent, I can then play with my efficiencies to get my SG and OG correct.
I've only done a handful of all grain batches, but I'm tuning in my equipment...and realize that it is a process that takes some time and experimentation. So far, I have undershot, overshot, and have hit the mark of my OG. All with keeping my volumes consistent.
Oh, and a Happy New Years to everyone!!
-Dan