Do a search on the web for dreamcast sites...
Dummy files being inserted into iso's was a big thing for DC...
Only flaw is, DC didn't use UDF, may have problems there...
If you use nero to burn your xbox games, you can just add a bigass file (mpeg or whatever) and set it's priority to high in nero, that will put the file at the beginning of the cd..
(please someone correct me if I'm wrong, because as I type this I'm debating if it's high or low priority that puts the file at the beginning of the cd)..