If you plant Black Locust next to them they will act as nurse trees providing nitrogen in abundance and quick shade to help them survive.
If you do that, plant them on the western side of them.
Discussion
Cool! The 2 rows of chestnut are planted east/west with ~25ft spacing and ~40ft between rows. I've got some black locust in pots. I've got black alder seedlings sprouting soon hopefully maybe those would work similarly. How close do you think I should plant the locust? Should I just put one halfway in between each chestnut?
Yeah. Halfway in between with the last one on the western end.