I had to make some window coverings to insulate some north facing windows with a very heavy, very thick boiled wool with coating on one side. The windows are 6 feet high by 4 feet wide so not small.
The fabric was challenging to work with, kind of like bending plywood to sew on velcro!!! Yup you read it right, sew velcro on to the edge of this fabric which itself would not have been too bad except that I had only mm top work with there was just enough height to cover the window with a little lip to fasten the covering on the to frame with the velcro.
The other challenge I had was the amount of fabric, there was supposed to be enough for 6 windows so I measured and to my surprise I was 20 cm short (the client had the fabric already, the vendor figured out how much they needed) on one end there was a diagonal cut that made the fabric much less than previously thought. In the end some creative thinking, figuring and measuring I managed to make up the shortfall and cover all 6 windows! The client was very happy when she heard this. Below are some pictures of the fabric and how thick it is.