I was curious about this as my car also only has a 16GB card and it it was just ~100MB more space needed so after a bit of poking around I managed to get it to fit on my 16GB card by deleting a few other files (in addition to the usual language files):
In the folder "maps\00\cfg\mapcfg\" delete the highlighted files/folders (basically anything VW or Seat specific):
SEAT (whole folder)
VW (whole folder)
se_default.cfg
vw_default.cfg
You should be left with just the SKODA folder, sk_default.cfg and vw_man.cfg. I didn't delete the file vw_man.cfg as it was the only file what that name format.
It should then (only just) fit on to a 16GB SD card (14.8GB formatted).
Plugged it in to the car and after checking the files it didn't report any issues and seems to work fine, but YMMV...