It would depenend on the mesh. You might want to check your settings they may be to low to see the mesh.
You might also have to change the layer it is in as well.
Any scenery you add will always become layer 1 by default if there is default scenary for this area the mesh should be set at a level below the default level.
I usually put any mesh scenery in the scenery.cfg file at the very end of the file just add 1 to the last area and to the last level of the last line. By doing this you make sure that the mesh is loaded after everything else.
If you are not sure what I mean drop me a line and I will explain.
