The bulk update request #8011 is pending approval.

create alias light_belly (530) -> countershade_belly (726)
create alias dark_belly (126) -> countershade_belly (726)

Reason: The second one goes to dark countershading as well, but how could it be done?

It seems dark_belly has a lot of uses where the entire body is "dark", not just the belly, so wouldn't be countershading (or technically reverse_countershading). Many light_body posts seem to be better tagged countershade_torso (which includes the chest and can optionally include the neck, chin/face, crotch, tail, and thighs).