I don't think it will sag....because of the way a shower curtain is hung - the hooks are only say 6 inches apart - so there is no "sag" allowance. I made my cotton shower curtain with a large (24") appliqued Texas star in the middle and it doesn't sag. As a suggestion - why not pin it to the curtain - hang the curtain - and see if it sags....IF it does - i'd just add button holes and double the number of hooks/hangers.