I'm surprised that the fabric stretched with your DH handling it. After all, we handle those leaders a lot while quilting, including sticking pins in them and tugging on them. Regardless, I think it would be easier to just make new leaders. If you try to salvage the old ones and it doesn't work, you will be making new ones anyway. I don't know if anyone has successfully used muslin for leaders - it seems to me that it would be too lightweight and might stretch more than the canvas. I don't think the new canvas/cotton duck would be too expensive. I remember buying some to make leader extensions, back when I was trying Velcro extensions (didn't like that much) before I bought Red Snappers.