Hello tonytamuf,
If you could try to use a DVD burner that sets the DVD+DL disk booktype to DVD-ROM, I believe you can easily copy your navigation DVD disk using DVDDecrypter ISO Read/Wrire capability.
Some of the DVD burners that let you set book type are BenQ 1620/1640/1655, Plextor 716/740, Sony DRU-810A etc ....
You can pick up a OEM BenQ 1655 at Newegg for $53.99 :-
http://www.newegg.com/Product/Produc...82E16827101006
They also have a retail SONY DRU-810A on sale which is a re-badged BenQ1640 :-
http://www.newegg.com/Product/Produc...82E16827131261
Typically you would select the .MDS file to burn with DVDDecrypter since this is the file that contains the layer break information.