Ah I think I found my mistake now...
.pak extension is used when copying files FROM WRS...
The type of the file doesn't matter. Because it's just using the file for saving the files.
You can make it like: .cowabanga or .firoball or simply .pak . (And even blank!!)
And so on...
Bullsh!t.
Have you ever dared to even take a look at the manual??
