I have the propane version in my 31' sailboat. Keeps it nice and warm when sailing in the high 30s to low 40s F (2-8 C). I have it mounted on a stainless steel plate that keeps the back of the heater about 5cm from the fiberglass.
The fan is fairly quiet. Once the boat warms up we shut off the fan and run the heater on low to use less battery power for the rest of the night. Double walled chimney works well, although the cap is large, at about 15cm, with three inverted bowls on top. These keep the inlet and outlet air separated.
The heater came with the boat. If I were to do it from scratch I'd get the diesel/kerosene burning version verses propane.
Curious what you plan to do with it.