I do love your board. How did you find it played? Did it 100% need to wide open main street or would the slightky more restricted side streets have worked just as well?
This was played on a 6x3 (roughly) while the rules call for a just a 3x3.
In Gangs of Rome the Mobs definitely require a decent amount of open space and you should ensure their base can at least fit into areas.
Very narrow side streets don't suit them well in my opinion, and cause them to bounce back and forth like a pinball.
I think the best layout for a GoR table would be a generally open plaza in the center.