I put mine (G3X OAT probe)in the side of the fuse, aft of the wing spar, inside the wing root cavity. I tested it today against a k-type thermocouple. It started from a soaked hangar reading 3F low and stayed that way through taxi, climb, cruise and descent. Flight legs allowed sunny side and shady side, no difference.
The K-type was located on the opposite side of the plane, 36" out from the fuse and 6" aft of the wing spar. An open bead style 1" from the skin.
Using a 3-leg ASI calibration routine (twice), the TAS was within .12 kts of the GPS. The OAT reading is possibly off setting some other variance. Never the less - the data indicates that" 1. the RTD is lower than actual, and 2. the location provides adequate tracking of OAT for flight.
1st Flight 1-27-18
Phase II 8-3-18