My alternative idea for the hanging involves manipulating the long length of fabric. Sian suggested looking at gathering or pin tucks so photo 1 shows two trials of gathering with deliberately uneven rows of stitching pulled up tightly. The top one is an offcut with the stitches running vertically, the bottom is one end of a 'spare' full length with stitches running horizontally. I like the effect but it has two problems - 1) drastically reduces the size and 2) could be any randomly dyed fabric.
Before leaving the samples, I rubbed Markel sticks over the second one (top in photo 2) and then undid it (photo 3).
Phot 4 shows how it looks when the fabric has flattened out - you can just see streaks of paint.
This didn't look very impressive but it gave me an idea to try random pintucks as I liked the scrunched up effect before the gathers dropped out. Photo 5 shows a sample on the same piece of fabric. I tried to use the pintucks to emphasise the curves in the design. I realise I forgot to show the scale in this photo, but the fabric is 34cm wide before stitching and the photo shows about 60cm of the length. The colours have slipped in this picture, in reality it is more of a green/blue. Photo 6 shows more of the length with the stitched part at the top. I think this is my favourite as it keeps the design but makes it more dramatic. Although it will change the shape, it should be possible to retain the general proportion. I think the shaped edges will make it look more like a crack in the wall (or floor), contrasting the serenity of a church with the storms and chaos outside.