I tried syncing the flac/PCM files to the NTSC GOUT and didn't have any luck either. What I did so far is just convert the native AC3 file to wav and tried to sync the beginning of the PCM track with it. The PCM track needed like a 1.176 s delay(note the number is off the top of my head and may be off a little). I'd fast foward through the remaining track and they got out of sync after some time.