Taken from this lecture by Jennifer Mace (part 2 of a 2-part series on ancient Greek art):
Here is a chart with human proportions, ranging from the normal through the idealistic to the heroic. Sharing here in case it might help anyone out there drawing or converting, given that heroic proportions is the name of the game for most things Warhammer.
But of course, all this silly longshanking is nothing compared to the perfect body shape: Spherical. Rotund, short, without visible knees, and with an enormous beard. Now that is perfection.