Merging VOBs from a 2-DVD set before encoding

[osullic]

I have the 1956 movie Around the World in 80 Days on DVD. In fact, I have it on 2 DVDs. Half the movie is on the first DVD and the second half is on the second DVD. I'd like to make a backup of this movie to one Xvid AVI file if possible.

Should I have any concerns about using VOBMerge to merge the VOBs from the two discs, before then encoding the result to AVI? Does it have any impact to merge VOBs that are not the same bitrate as each other (which is the case here)?

Normally the IFO file gets loaded in Auto Gordian Knot. If I merge the two VOB files, should I just load the merged VOB into AutoGK and forget about the IFO files?

Thanks for your insight.