You know what actually I think I managed to get it working with the k4os lz4 nuget package. The trouble I'm having now is that when I call PackageWriter.Write it opens a stream to the lsv file and then iterates all the files in the directory (including the lsv file) and throws an error because it can't open a stream to the lsv when one is already open (at info.MakeStream() in WriteFile. Perhaps I'm trying to package the wrong sub-directory?