Did you do everything as I've described above?
Mapsource is an old and unsupported program for those complicated maps.
I've downloaded and used TOPO LAT.rar from post #5
This map has embedded digital elevation data in every sub-file (tile), so it can be displayed in 3D mode in devices and Basecamp.
Below is the gmapsupp.img (Topo Lat.rar) as it's displayed in a nuvi connected to Basecamp in "both 2D/3D" mode and the other screenshot is the "Mapsource installed" mapset with contour lines (gmapsupp.img+OFRM_IZO.img from Topo Lat.rar)

gmt07