In 3590 i've transfer these folders:

system\JCV\ to sd:\garmin\JCV and it work fine
system\gmap3d.img to sd:\garmin\gmap3d.img and it work
system\ASR\ to sd:\garmin\ASR and it don't work
system\SID\ to sd:\garmin\SID but i don't know if it work

in garmindevice.xlm in fact just for JCV and gmap3d.img there is "externalpath" string.
I think that SID don't work because there isn't "externalpath" string but:
- if i change garmindevice.xlm and i write "externalpath" for ASR and SID folders, do you know if it work?
- like i must test if SID work? (in menu is always possible set ON or OFF inside nuvi or inside sd)