how much space is behing the inner skin. I want to add extra deadening to the outerskin but don't want the window glass to catch anything.

You can easliy get a layer of sound deadening on the back of the door skin.

thanks for replying.

i would like to add 2 layers on the outer skin, 1 layer on the inner skin, sound diffuser (about8-10mm thick) and some moistuer guard, altogther about half an inch on the outer skin.