Not sure if I explicitly discussed it there, but I consider it by-and-large settled there.
This is about the rationale of where I want to put the Golem-boosting buildings. Currently we have one set, the Fire II one which must clearly be set at Elementalism (well, Sorcery but via Elementalism). The two promotions which I want to offer are Heavy and Light, so we want to put them at one of the 3 remaining techs. Of the three, Divination is easily the most useful for players (especially Luchuirp, with Dwarven Druids around the corner), so I want to place the buildings at Alteration and Necromancy.
So what mana at each works well with Heavy and Light?
Body at Alteration gives us Light, but what do we do for Heavy? Personally, the mana that goes best with it is probably Death, but I could be persuaded to any - honestly, it's a hard decision with none really fitting with it.