Create folders named "movie one", "movie two" etc. In each of these folders, create a folder named "video_ts". Take your DVD files (.bup,.ifo,.vob) and put them in the appropriate "video_ts" folders. Keep the titles separated!
Recode 2 will allow you to import these files. Choose "remake a dvd", select "import titles" , navigate to the folders you named "movie one" and such, and you will be pesented with the titles you created. You can then use this method to put them all on one DVD; even if the files you made need to be compressed to fit.
This method doesn't let you keep working menus, however. But it didn't sound like you needed them.