Some thought will need to be put into this section on how to deliver it’s purpose. First this exists because the length of the story had to be taken into consideration. And where these memories and experiences are vital to who Emerson and Preston Brooks are, what they mean to each other, and how they developed their bond; it was better to keep them separated from the main story as a way to continue it.
One potential avenue could be, corny as this may sound, is that readers specifically request to learn more about specific experiences. Now this can be fun because one, they may have already been written and or two; they may not be at all but be a fun exercise in revisiting these characters past and giving you additional new content.
Either way the attempt here is to interact with followers who would like to engage with each other as well as the author.