It may be better to play it safe and write a program that trawls the Filestream table and extracts the files with the OpenSqlFilestream API and writes the file and the metadata. Yes, this means that you need to find a programmer that can write such a program. Then again, this is not 200 lines of code.
This also gives you a consistent view of the contents. If you read the raw file area directly, you will get old versions and deleted files that have not been garbage-collected yet.