It seems .dmgpart is currently the only way to get a folder over 4.4GB onto DVD-R. That's not an option for me because
- during backup and restore all parts have to fit on the hard drive at one time
- when one medium fails even the data on the remaining DVDs becomes inaccessible
How about copying to one regular .dmg until it's full and then starting a new one? Some folders may be split but could be merged on restore (except using Finder).