You can not open a 4.50 file in Version 4.40. (This subject is discussed on this Forum almost monthly. Use the [Search] facility to review past posts on this topic.) Typically the file structure changes due to added data in the newer version.

If you want to try to manually manipulate the data using the neutral file, you're free to attempt that. What you have to do is compate the documentation on the neutral file between the two versions you're dealing with - let's call them "older" and "newer". You need to find all of the new data in the "newer" version - say for example the "reducer section" - that doesn't exist in the "older" version. Then using an "Editor" (hopefully not NotePad), manually delete this "new data" from the netural file. Be aware that if any of this "new data" pertains to "element data", then you will be deleting information for each element in the model. One extra, or missing, line and the Neutral File Reader will be unable to process the file.