First post to this mailing-list. yay!
DVD-o-matic is a very nice program, that I hope will grow to be even greater. I will try to help by raising some discussions.
Something I thought might improve on the DCP-size is to enable quality-based JPEG2000-encoding. OpenJPEG has an option to do this (-q according to documentation), with a value in decibels.
Does the DCP-standard accept VBR-files? My web-search found no definitive answer.