Just stumbled across this old thread (noticed it in the Tutorials index actually). Seeing it's in Tuts, here's an update to the above:
With recent fw updates all 2xx[W] and 2x5[W] series now support 2 image files in Garmin folder on SD, named as gmapsupp.img and gmapsup1.img only. Also applicable to 465 & 7xx nuvi series.