I think you're missing the point. For both the efforts I've used to turn off device driver signing, installing the drivers shows them unsigned. I'm thinking there is a flag in my registry that has already defined that driver as unsigned and I am unsure how I can unflag it.
In other words, if I could wipe the slate clean, disable device driver signing, then install them, I think I'd be ok. But as it stands now, every time I try to install them, even from the method you described, it's still declaring them unsigned.