Sorry, I was wrong. What you actually want to do is edit dosbox_privateer2_single.conf in Notepad.
Second to last line says: dark
Change to: darkfix
Apologies for the confusion, I thought the exe loaded from the shortcut initially.
Hmmm, I made the edit for the file. Now running the launcher from the shortcut opens DOSBox for a moment and then it closes with nothing happening. DARKFIX .exe is in the same directory as DARK.exe., so by all rights it should work. I'm going to try downloading and copying the patch fileset back over again, in case there was some corruption somewhere. I've copied the text from dosbox_privateer2_single.conf here for confirmation.
# Lines in this section will be run at startup.
mount c ".."
The launcher worked fine for the DARK.EXE so I'm not sure why it won't launch DARKFIX.exe. I can say there is a difference in file size between DARK.exe (956kb) and DARKFIX.exe (868kb) although I don't know if this is by design by the patch writer.