I have camped in some pretty big storms and the factory privacy screens do nothing to stop the canvas (and then matress) from getting wet. I got my canvas cover made up before a big trip last year, and it works a treat at keeping the camper canvas dry. Also a noticable difference in the insulation in winter.
Down side with mine is if you use it in a summer storm, the van gets way too hot, as i can't get the air circulating. The one with the windows looks like a much better idea. My one attaches with press studs only and have a habbit of coming undone in heavy winds too.
For me, the ones on the website look like perfect solution, and i like the idea of the sail track, so easy. Hope someone gets one and can give some feedback on the forum.