But, what I really want is an even deeper transparent archiving mode. I compressed a sample of 20 GB of those same raw files with 7z LZMA2 on Ultra and got a post compression size of about 83% of original, so the LZX compression MS offers (but hides behind a command line tool - out of site of most users) is leaving 10% on the bone. Implies if properly implemented, I could have 421 GB of space freed up.