The rain fly for our wall tent has always been the clear heavy duty plastic stuff you get from Home Depot to cover floors and furniture when you paint. We setup the tent, put the rain fly over it, cut a hole a little bigger than the opening for the stove jack, and we're done. If the plastic is to close to the stove jack it'll melt, so in reinforces it's corners on it's own. We normally replace the rain fly every 5-6 years.