This is a main type of glyph in my catalogue. It looks like a fusion between the splendid bird and the tired old bird:

However, here there is 'tiredness' in two directions. Moreover, there is asymmetry between left and right. In the glyph Eb5-29 this is most evident in the wings of the bird, the left (as seen from us) is shorter than the right. Other glyphs of this type also tend to show a shorter left side.

Remember the glyphs of Sunday (in Large Santiago):

Hb9-17	Hb9-18	Hb9-19	Hb9-20	Hb9-21
Pb10-29	Pb10-30			Pb10-31

I guess that Hb9-19--21 together corresponds to the double-headed bird. That would explain why the corpse in Hb9-19 not is hanging straight down. It is equivalent to the beak towards the left.

I also guess that the double-headed bird means the three domains of the visible sky: that in the direction where the sun is going up, that where the sun is at its strongest and that in the direction where the sun is going down. Could this be an explanation of manu mata e toru?