That's why I use split mode, so I don't lose quality, and then I copy all the extra materials onto disc 1, unless there's not enough room, then I put them on disc 2.
Maybe they'll add a "Disc won't fit on DVD5, would you like to clone in split mode?" or a customized split option where you can add in the extra bits.
This is a recent development, I've been doing this for a few years now, splitting with DVDFab & burning with Nero (not with DVDFab using the Nero engine) with no problems.
For all I know it could be a software conflict causing it, I hope to sort it out before too long, might be after my next HDD format though. hehe
Thanks for your input. I'm trying VSO's CopytoDVD now, so far it's burning.