Let’s assume for a moment that you accept our contention (Taylor et al. 2009) that, since extant terrestrial tetrapods habitually hold their necks in maximal extension, sauropods did the same.  That still leaves the question of why we have the neck of our Diplodocus reconstruction at a steep 45-degree angle rather than the very gentle elevation that Stevens and Parrish’s (1999) DinoMorph project permits.