Just FYI for those that are wondering if one dual layer DVD can be created to combine Region 1 and Region 2 DVDs...

I spent some time looking at the configuration files and directories on the two DVDs. They have exactly the same directory and file structure. I looked into the data in the files that I could. I found that all the navigation data is stored within a TABLES directory with the same set of 218 file names -- so that's biggest problem. After editing some files and renaming some others, I combined the two DVDs which resulted in 4.70GB of data (a single layer DVD maxes out at 4.30GB). The dual layer DVD that I created was not recognizable as a navigation disc though.

I'm not saying that someone can't figure out a way to combine this data but I can tell you it'll not be a trivial matter...