Free: Contests & Raffles.
I have a 15x24 that I use a Cylinder stove in and had the same problem. Two years ago at the sportsmans show I bought a wood pellet feeder attachment that they make for it. When we used it this year I used the wood to get the tent warm before bed, all the corners and equipment and then used the wood pellets through the night, it kept the chill off and burned all night long. In the morning we stoked up the wood to get it toasty in the tent again but the pellets kept the chill off and kept me from having to restoke the fire in the middle of the night. A 3/4 of a bag of pellets lasted all night and they are cheap and clean. I would recommend them as a good option.