mr heater sunflower mod
Even with my Buddy heater I always leave the door unzipped at the bottom and normally crack open a window if I don't feel the top vents are letting the air out enough. This might be a good solution to your problem of being too hot as well. I know a lot of people use the mr heaters and have for many years and I am sure most have never had a problem with them. I have seen some malfunctioning ones before and have friends who experienced minor CO poisoning from one.
If you try to adjust your heater please be sure to have good ventilation in your shack and consider bringing a CO detector.