Command line -dc rom launching issues (no spaces or character limit??)

Sorry if this is a repeat of another thread, but I couldn't find anywhere else on the web that mentioned this issue.

I'm able to launch dreamcast games via the command line with
"demul.exe -run=dc -rom=pathtorom\Rez.gdi".

However the launch only works if the rom has no spaces or underscores in the name so:
"rom=pathtorom\Sonic Adventure 2.cdi"

will not launch but renaming that to "sa2.cdi" and typing:
"rom=pathtorom\sa2.cdi" will launch on command line no problem.

Also, rather oddly: "rom=pathtomrom\Sonic_Adventure_2.cd " will also not launch the game.

I have no problem loading these roms with the GUI. But I am trying to configure Demul to work with Ice and Steam, and that requires a command line launch.

Is this a character limit, or an issue with spaces or underscores? Perhaps I've done something else wrong elsewhere in my set-up.

Any advice or thoughts would be greatly appreciated!