Got the little bugger, LOL!
The right texture is not the one mentioned above but the one named " Torp.tga " located in the path C:\SH3\data\Menu\Gui\Units.
Simply edit it to render the texture fully transparent with an image editor ( Like GIMP for example ).
Don't forget to save first a backup copy of the original file in the case you want to revert back to its original state.
