[ffooky]

If both VIDEO_TS sets have menus that you're keen to keep then you have no option but to keep them on separate discs, though you can always fill up the unused space with any files you like in an EXTRAS_TS folder which would only be accessible with a computer.

If you're not bothered about the discrete menus there are many options depending on which OS your using and which software you have so you need to make that clear.