I also have a Mr. Buddy heater. I have a 2-3 man hub and a clam Kenai, at first wasnt sure which i needed either the 4,000 to 9,000 BTU or the 9,000 to 18,000 I do believe thats what the bigger one is, but I went with the 4 to 9,000 BTU and i tell u what on high in the hub i was comfortable all day and on low in the Kenai. As for my comfort level being fishing in my snow bottoms and a tee shirt. prob bout 65 degrees to 75 degrees. depending on weather u can also b good in the hub on low i just like being xtra cozy. hope this helps.