Tom and others: Here's a good thread to reference.
http://www.thesamba.com/vw/forum/viewto ... sc&start=0" onclick="window.open(this.href);return false;
Here's some pics with measurements, sorry they are in inches (we don't use metric).
Back section
You can see in the pic the white velcro strip, it mates up with the two sides, you have to make sure if you add these that they are sewn on the correct side of each piece and the the correct piece of velcro will match up to its opposite piece.
Both sides are the same dimensions just the opposite

Both of the side I made are longer than what is stated in the thread, because they under lap the fron and back pieces to join by velcro.
Front section

You can tell by the dimension at the middle bottom that there is a curvature, its slight but follows the roof line.
I am No seamstress!
The side pieces are the hardest to make without a pattern to go by. They are no square and even the back is at a slight angle. I would suggest a mock up of card board to get the angle correct.
Hope this helps and if you need pics let me know.
Tip: Use heavy duty sewing needles and good thread!