Being new to the hammock scene, I have lots of questions. But I will start out small. Right now I am in the process of turning my tarp once used as a tent into a rain cover. I have attached PMI cords 3 m in length to the corners, the 'head' and the 'tail'. But looking at it now, it seems like the cords are too long for it to be of any use. Whats the optimal length for tarp cords? Should I reduce the length?