Bemerritt, I was thinking of using something similar and if there was room, in conjunction with this entry gland that came with my kit.
I have a Savana too and know of people routing the wires through the third brake light and/or also the trim piece that has been talked about above the brake lights, but wasn't sure it was worth it.
I know guys are cutting and drilling into their roofs all the time, but I just haven't come to grips with it yet.