Audio Synch probs while using ?correct?? setting

Hi, I just encoded a great AC3 rip of a movie. I used the delay settings given by dvd2avi as it demux'd the audio track but my lips are slightly wrong. Ive played around and I believe I have to use a correcting (redelay) of -27 ms to get it almost right. However its not quite right, This is the first time that dvd2avi has not given me the correct delay for synch. Has anyone else found problems with synch using the preposed delay from dvd2avi. Could doing AC3 rips mean chosing a different delay to account for decoding/processing the surround info? Current settings: preload 500 ms audio Interleave audio every 2 frames Thanks

delay 

Ill try using smartripper to demux, maybe that'll be good right now I use Cladvd XP, and smartripper for finding those neeto Dolby and DTS trailers hiddin in alternate angles