There is an expression I am trying to think of...Thats it - DOH!! What a maroon!
For some reason I got it into my head that because of the new file structure, the sounds needed to be within each asset that you wanted to mod. I spent 3 hours + on Tuesday modifying all of the sounds reference files to point to Krellnuts Wagons folder which I had placed inside the Cabforward pack audio folder, only to find out after talking to Bwfer yesterday about how he tackled it with his video clip, that the Krellnut sound mod works exactly the same as it always has. Just follow the instructions and away you go...
Oh well...
G