And, anyway, for northmen everyone south of the Neck is a southener, imo. (with the rare exception of the men of the Riverlands, in the period when they are actualy allied with the North maybe) So, crownlander sounds kinda weird, but southener is a bit too broad a term to be used.
Tried hart to actualy be useful and give advice for naming the Manderly culture, but to no avail. Men of the White harbor? Harbormen (even weirded than crownlanders) Or, maybe, pie eaters?

