There is a new xmash 0.7 that works with that mono file, but it works fine with toway.
The fsb is indeed encrypted: Key is DFm3t4lFTWDFm3t4lFTWDFm3t4lFTWDFm3t4lFTWDFm3t4lFTW
xmash won't automatically attempt to decrypt it because the file appears to be truncated, the size is 0x951bae0 bytes but this file is only 0xa00000 bytes.