Basically all of you are correct. The tail lift is usually not considered in the total lift merely by convention. The equations/curves used to develop stability and control and other performance parameters take this into account because they are derived using wind tunnel or CFD data. When designing a modern airliner or military airplane the above method is used for preliminary work and once a configuration is chosen, then detail analysis of the contribution of every part is performed (costs a lot of money and requires many computers and engineers).

cirrus
Aeronautical Engineer (among other things) and RC newby