For those that are interested, here's a description of the interfacing I used:Pelmet Vilene
(New Zealand) Extremely heavyweight interfacing used to make valances for window treatments. It is very sturdy and will not wrinkle when sewn over repeatedly in the same area. Timtex (US) used for making fabric bowls is the same thickness, as is Pellon #70 interfacing. As a thickness comparison, take a piece of paper you use in your printer, fold in half and half again and half again. This will give you 8 small divisions. Run your thumb and fingernails along the creases to make them really sharp. The thickness of this fold should be the same as the interfacing.
Hope this helps!