Just a thought you might be able to attatch a fixing point/loop to the outside of the inner half way along the slope/where sags, then lead a cord from that point to one of the tent pegs and tie it so it's taught.A slight trick i think they missed with this tent is there is no way to tightening the sloping sides of the inner, especially the rear/head slope, it sags a bit too much for my liking so i think there is going to be my first tweak.