We have used our Propex Heater many times and absolutely love it. We left for our trip in November so the weather in Vancouver was chilly. The Propex HS2211 has left nothing to be desired in the way of performance, it easily heats our trailer and then some. Leaving the heater on all night obviously ensures that you use a fair bit of propane
but considering the heat output, temperature differential and lack of overall insulation in the older Trilliums it performs extraordinarily well.
I would also recommend this model as having the option to mount it outside saves a lot of space. Fabricating and mounting the frame and skid plate took some time but was well worth it for the space we saved inside. I also used both the fiber and insulating tape exhaust wrap to keep the heat in the heat and return forced air vents to optimize performance as much as possible.
As for mounting location, we chose behind the axle
tucked up as high as possible while still maintaining clearance to the floor. The wiring and heat runs enter the floor beside the water storage tank and enter/exit the storage compartment under the bench. We mounted the thermostat on the opposite side on the rear facing wall of the closet and it seems to be an adequate location for its effective operation.
Hope that was helpful.