If I wanted to create an "add-on" romset for a previous version of MAME, how would I go about doing that? For example, I have a complete set of 0.96 ROMS and a Rollback set that represents all of the ROMS removed in previous versions. I want to create a set of 0.67 ROMS that ONLY represent those that cannot be found in the 0.96 set. Using Rebuilder with the 0.96 set and the 0.67 set folders as ROM folders and the Rollback set as the "add-in" directory. This only partially finishes it. It picks up games like gauntlet, but misses some like 720, Altered Beast, and APB. I know i can create a complete set of 0.67 ROMS, but I really don't want to duplicate any diskspace usage if I don't have to. Any suggestions?