You don't want to put it in the lower hose.
I'm sure there is another location that will work. Is there an oil cooler that uses engine coolant? That would normally be on the back side of the thermostat.
Poke around there has to be a spot.
Mike
Yes you need to be on the other side of the thermostat. What you are measuring is only the coolant outlet temp. It's not going to read much of anything until the thermostat opens.
Mike
I would not worry about 207. As for the location of your sender, it must be located in the loop of the engine that circulates when the thermostat is closed.
I'm not familiar with the engine you have but typically coolant circulates through the head and heater core and sometimes a portion of...