Just saying that DN3D doesn't have any 1-6 menu in its main menu so I have no clue what you're talking about.
Yeah, I know DN3D didn't have that menu, it only exists for the Shining level. And it isn't on the main menu, it comes up when you execute the REDRUM.bat application from the DOSbox command prompt.
The download contains a batch file intended to launch DN3D with the command line parameters needed to start the custom level.
Probably doesn't work because you have to run DN3D through DOSBox. The batch file is written for an old system where DN3D would just work.
You should be able to get it running by editing the dosbox.conf file. Near the bottom, you should find something like this:
# Lines in this section will be run at startup.
mount C "."
Easiest is probably just to change "duke3d.exe" to "redrum.bat" (change it back when finished, of course).
I think you can also launch custom levels using the setup program, but I'm not sure about that.
Or you can use eDuke32 which has a level / mod selector.
thanks for the help, I'll try it out a little later on tonight and see if I can get it going