my little barrel stove is a Sotz round door kit on a 15 gallon drum cut off at the second ring. It heats a 9x12 walltent. With your big tent you'll need a 55 drum if it gets to single digit temps. A 30 will have to be kept burning at a good rate to heat that space, and may not go all night. If you can find a Sotz kit, rather than Vogelzang or US Stove kit, they are airtight and much more efficient.....
