Hi all, I'm going on a 3 day trip to Dartmoor this weekend and as I'm not sure exactly where we'll be I might not be able to use my usual hammock/tarp setup. So it's ground dwelling for me! I have a 3x1.5 tarp Unsponsored made, and was planning on using it with just a roll mat and sleeping bag, the question is...as it's fairly open, will it be a good idea to also use a bivi bag?