After reading ATULIN's posts a few months back about installing insulated blinds in his Sprinter, and feeling the sun pouring in all of the windows in my 158" '06, I decided to look into these blinds and ordered a 48" long honeycomb insulated blind from Amazon for about $35.
http://www.amazon.com/gp/product/B008OPVEV2/ref=oh_details_o08_s01_i00?ie=UTF8&psc=1
The two sets of rearmost windows in the T1N 158" are about 52" or so inches wide, but for mounting purposes, there is about 49" of flat sill on the top of the windows- just enough to mount a 48" blind to. I quickly realized part of the reason why ATULIN had tracks on the sides- to keep the blinds from flapping around as you drive.
So pressed the blinds all the way closed and used a 1/8" drill bit to drill through the blind at two spots, each about 6" in from the ends. Then I fished 40lb test fishing line through the 1/8" holes and tightly attached them to top and bottom sills with self taping screws. Then I used more self taping screws to secure the top of the blind to the top sill and VIOLA! I have blinds that block most of the heat and light and they travel up and down using the guide (fishing) lines. If you look closely in the photo, you can see the guide lines and holes right behind the driver's headrest. They also have some sort of mechanism in them that allow them to stay where ever you put them. Up, down, in the middle, where ever. So I ordered 4 more and installed them in all but the sliding door window. The first window behind the driver's seat required me to cut them to fit, but it was easy and the rest of the installation was the same.
Going on a month now and we are very happy with them. Notice how the two girls (baby in first row- you can just see her toes and 3 year old in 2nd row) are both in the shade, even though I'm parked in the full sun- although some light is getting around the edges, so it's not a dark cave in there.
Also, if you look closely, you can see that the roof has a headliner only till about halfway back. I'm in the process of putting in the other half of the headliner tomorrow. I ordered grey corrugated plastic from a local sign shop. $20 a sheet.
All in all, I'm really happy with the way my new Sprinter is turning out.