As far as I know, the HU volume control has no effect. You close the door on the cord to the PC, you would never get the window tight enough.
Other Imprint hints here:
http://www.diymobileaudio.com/forum/diyma-tutorials/50129-imprint-tuning-hints-tips.html
Other Imprint hints here:
http://www.diymobileaudio.com/forum/diyma-tutorials/50129-imprint-tuning-hints-tips.html