Step 2: Slap it up in the van
I started by measuring up and making a cardboard template - not pictured. Then I cut the reflectix to fit.
I did the next part at night so I could easily check for light leaks.
I taped it up and started sticking 1" velcro strips in the corners and working inwards to see how much would be required. The corners were not enough, so I stuck more strips in the spots where any light got out until it was completely invisible.
The second pic shows the placement of the strips that kept the light in. A bit uneven, but it was necessary to do it that way to contain the light.
Then, you will realise some of the strips aren't sticking that well. Carefully take off the reflectix, holding the van sides of the strips down while you do, and then smooth the strips down really solidly to the van.
Put the reflectix back up and don't mess with it. The strips take 24 hours to cure.