Well, I have a bat file in my M2TW folder which points at a new config file which has the features line in.

Then there's a mymod folder with a data folder inside - which in turn has a sound folder with the two files I specified and a world folder with the normal tree down to the base and campaign folder.

Then I added a modded edu file - and launched it through the bat and the changes showed up...

All it should be doing is reading the files in the mod folder in preference to the (packed) files in the main data folder.