"That's what I'm trying to figure out," Billy replied, turning the book to point it up at her. "The mechanics look simple enough. I just wonder if they're strong enough to support us long term. Not to mention the other problems it's brought up."

He looked over his notes one more time, just to make sure he had it all right. "I'd be wasting an opportunity if I didn't try this sometime," he noted, tentatively flexing the wings.