If there is a way to save a file in old vtk 3.0 format(except using an old vtk version)?
If saving method has no serializing versioning, I guess there is no way to save it in old version. Have you consider to save your file as another format, like png, bmp, whatever, and then import as you need in old version of app ? I know, it is a long way to do that, but it is a workaround.