Here is the original thread. Unforutanely the pics have been deleted. Turns out the cable doesn't stretch, but apparently a small plastic guide breaks causing the slack.
http://986forum.com/forums/general-discussions/25704-window-regulator-permanent-fix-stretched-cable-3.html
I see there are some pics from some others on this forum in the thread and the link on to how to remove the interior door panel, so this thread should give you an idea of how to fix it.