From Nextgen select "content/schemes/nextgen day(nextgen night)
Copy these and paste into the same folder in Primo 2.4.
For TTS to work you must modify the voice directory in the "voice" folder.
The roads can be made wider by including the "width_road" plug-in in the UX folder
The fonts for road names can be made larger with a simple "sys.txt" entry.
Different skins can only be used by changing the plug-in in the UX folder.
Are you using WinCE or Android?
I use nextgen v 543580j with the skin_nextgen_by_pongo. This is very like Primo 18.104.22.168.13.405512 running with he DimkaWA_P_174 skin.