I have a PL that I will use over the RL of my HH then tie it to the tie out points on the HH. I do this if it's going to get colder than what I was expecting. Be sure to not cover where your head is or you will have condensation issues.
Also worth noting is I don't back pack but motorcycle camp so weight is a non issue. If I were hiking I would find something lighter to do it with or have a jacket do double duty.