They require a texture.cfg file that contains something like this (from the -100):

[fltsim]

fallback.1=..\texture
fallback.2=..\texture\spec
fallback.3=..\texture\bump
fallback.4=..\texture\night
fallback.5=..\..\..\..\Scenery\Global\texture
fallback.6=..\..\..\..\..\..\Scenery\Global\texture

You can copy one from the texture.xx folder of the model you put it in (e.g. the CS_B727-100\texture.aa or CS_B727-200\texture.aircanada etc..).

Make sure the names of the textures are correct by comparing them to other default textur.xx folders. They should be, but they will BMP instead of DDS. ;)

Mark