REFLEKS HEATER - How big?

[Onemoreproject]

Hello,
I am refitting a 36' cold molded (wooden) boat and want to install a Refleks heater. Why Refleks? Because of there reputation for reliability and trouble free operation and no electrical dependence.

My boat has a 15LX10WX6H= 744 cubic feet in the main cabin that with a 2 quarter berths with only curtains separating them from the main cabin. They add an additional 7x8x4= 174 cubic feet of volume. I have low expectations about how much heat will make its way forward into the head and vee berth. Although if we are sleeping in the vee berth, I will direct some heat that way with fans.

The heater that has been recommended to me is an MK66 that puts out 5500 BTUs. They burn most cleanly on high. I am concerned that a larger heater will be uncomfortably hot at the lowest setting and that when they are turned down, they don't burn as cleanly - making soot and needing to be cleaned more often.

If anyone has experience with a Refleks of any size I would like to hear about it.

Thank-you,
Onemoreproject