For me, it does not even work at 15 meters. I see no custom POI at all. Not even those in Extra/Custom POI.
Update: it does not work with CHN version 220, but it works with Sg/Mal version 250 at 80 m and less. Thanks Garmin!
Another update: Even with the Sg/Mal firmware, I see the symbols on the map only if the POI bitmap is made in 256 colors. If I use 24-bit or 32-bit bitmaps, the symbol is not shown. Yes, it does this with EPE and POI Loader. With the CHN fw, the same files do not show any symbols... :(