Stephen, if you like something like "ready-2-go", you can have a look at simheaven.com and download OSM sceneries for all continents, even photo sceneries for Northern America (see http://simheaven.com/?page_id=322 and search for "(USA)") or any other photo scenery in ZL16/ZL17 of Europe. For adjusting visibility, you can edit any .obj or .fac file and search for "ATTR_LOD". The second value is the visibilty in meters. For the R2_library this is 8000, you can increase the LOD by changing e.g. "ATTR_LOD 0.000000 8000.000000" to "ATTR_LOD 0.000000 25000.000000", best do it with Notepad++, there you can change all entries with one click.