Many years ago an old "linebreeder" told me the true genetic level is like a calm level of water, the averages of a population. Back when I was measuring the distributions of an average, of course for every individual above average there is another below average. Heterosis/hybrid vigor is like the crests of a wave that will return to the calm level, a non additive situation which was further established by MARC research experiments. The difficulty is being satisfied with the true "level", the tendency is to either ride the waves in choppy seas or add more "water"