I agree with Charley in that being in the sun isn't much of a concern - unless you are sitting on the ramp and in that case you already know the temperature :-).  I put mine in the wing root fairing on the right side.  It is pretty close to the engine outlets, but seems to work okay.  I have found on other installations that it could almost just be thrown inside the wing someplace if it weren't for the heat sink of the fuel (the fuel temperature doesn't change very fast, keep the air around the tank at a temperature different than outside).  Protruding out through any inspection panel would work.  How about protruding rearward through the fairing ahead of the flap?  If it is one of the ugly round tubes you don't want it out in the airflow because of the drag.  I like the NACA inlet in the tail (on the ES and IV), but it requires a long wire run.  I don't like the cabin air inlets on the side of the fuselage (on the 320) as any leakage from the cowl is too close).  Lots of options.

Gary Casey