Funkilller! Now I'm gonna go pout! lolThunderbirds are not excited about the idea of being mounts. They might consent to bear a Solar if absolutely necessary, but you have a better option in your people's kites. The Thunderbirds can each keep many kites aloft at once, which was the main source of the Fayum's military strength.
I get it. I guess I'm going to have to try and focus on mounted archery for my horsemen, since there are places where cavalry will come in handy.