Nice to hear N=2. I'm really hoping Fable comes back soon.

In my case two people are making very-near-light-speed trips to a star 20-ish light years away. Originally, I had one leaving a month earlier and making the journey with a Lorentz factor of 40, while the protagonist takes the same trip at > 200.

The former experiences a trip of 6 months, the latter something like 25 days. And I wrote it as if that meant that the protagonist would get there months ahead. But both of them will take hours to a day over the time light takes, and the one who leaves a month earlier will get almost a month before.

That error sat in my manuscript for two months of back and forth with other models. Fable found it on the first go.

LMK if you want to trade manuscripts!