I agree 100% with the thermacell underlay, keeps you warm and dry while laying down. I'd still like a cot, I'll be off the ground (incase of a tent rain flood) or accidentally picking the ONLY lump/rock or whatever under the sleeping bag, that jabs you not matter how you move. A thermacell will still work on top of a cot; it'll keep the dew off the underside of your sleeping bag.
Speaking of lumps under a tent; we set up a new tent in out backyard, just to see how it went up. The kids and I were going to sleep in it that night. While Cathy (my wife) was laying out the sleeping bags, she finds this lump under the tent's floor about the size of a small pinecone. So I'm asked (told) to go under the tent and remove it. So I did and when I came out from under, I found myself holding a petrified piece of dog crap!!! LOL
Dan..