Nuvi 66 symbols

I like to go geocaching. While I have a Garmin Dakota 20 handheld GPSr for doing the actual searching for the geocaches, I prefer to load the same .gpx file on my NUVI to make it easier to navigate from one cache to another.

To load the .gpx file to the GPSr's, I use the GSAK program. GSAK allows me to assign different symbols for the different cache types when I send the waypoints to the NUVI. This is beneficial in that as I drive along, I will see the symbols on my NUVI screen and know at a glance if the symbol is a Traditional cache, a Mystery cache, a Mutli-stage cache etc.

I have loaded two previous NUVI's in this manner. A NUVI 260W and a NUVI 1300. In both of those cases, the symbols that I specified in GSAK were properly displayed on the NUVI. But that is not the case with the NUVI 66.

It appears that when the NUVI 66 loads the .gpx file, it completely ignores the <sym> tag in the .gpx file. Here's a picture showing the same .gpx file as it appears on the NUVI 260W and the NUVI 66.

What are the names for the symbols in the Nuvi 66, and how are the symbols entered in the .gpx file?