Brian,
Yep, I have done both. Tab does nothing, even if I have the prefer to "Face of Core". What I have done as a work around is use a thin line, move it to the location that I want to dimension, dimension that line to the face of finish, lock the dimension, then I delete the dimension, but keep things constrained so that if I do stretch the end of the wall, the line will move with it. I just wish Revit could do this but I have not been able to get it to work.
Is this the work around for now?