If the folder doesn't exist then create in the root of your 2555. The name isn't case sensitive or important and location of the folder isn't even specific. You can name it poi, Poi, POI, Cams or anything like XXX or even scatter the *.gpi files around in the unit or media card and they'll still be found by the unit. You can do the same in your 755 and also with MP3 files too with it.

Some files must remain in specific folders/paths but not GPI files.