Gb6-21	Gb6-22	Gb6-23	Gb6-24
12 feathers	13 feathers	15 feathers	15 feathers

Possibly the difference is that in G the quartet is located at positions defined by midnight culminations of stars (like Castor in February 23) in contrast to heliacal risings in the other texts.

Possibly side a of the tablets refers to heliacal risings and side b to midnight culminations.

I cannot claim to have solved the number riddles posed by the 25 + 30 = 55 feathers. A partial answer could involve, though, 55 = 1 + 2 + 3 + ... + 10. This number together with 6-21 (June 21) points at the end of the Sun cycle, because 55 + 172 = 227 (i.e. an allusion to 22 / 7 = π).

I now intend to begin a study of the Q text because it is the shortest (excepting G) of those with 'Bacabs'.