I'd like to suggest to add the following to CompressionInfo:
public static implicit operator CompressionInfo(CompressionType compressionType) { return new CompressionInfo() { Type = compressionType }; }
This would allow to write e.g.
writableArchive.SaveTo(stream, compressionType);
instead of
writableArchive.SaveTo(stream, new CompressionInfo { Type = compressionType });
while retaining the flexibility introduced with CompressionInfo.