When you only look at hubs, you’ll get nowhere. the biggest point of the last big industrial exlaneion was to get people to create and build things off of main routes and hubs. Everywhere.
Anyhow, relatee, even if only tangentially:
if you struggle with selling stuff, create demand yourself.
Example. You specialize on mining ships. You seek out wystems with certain miners in certain ships. you build there. you blow them up. (not the pod!), they buy it in local, from you.
this works for many ships, like exploration vessels. haulers not so much, because blowing up haulers results in blowing up the pilot’s reason for using the hauler.
i hope it helps somehow.