These are not the original files. The original SHNs were decoded and then burned to audio CD with CDRWin v3.8b, so no write offset was employed. The current FLACs were created by extracting the tracks from the CDR with EAC v0.9b4 and encoding them with FLAC Frontend 1.7.1 Etree edition. So the current source info looks like this:
CSBmod > M1 > DAT-M > CDR-2 > SHN > CDR > FLAC [ > CDR-4 for you ]