The Turbo Tru Turn claims to be tested to work in lowering temperatures. HobbyKing has the plastic ones similar to above in the international market, so easy enough to obtain and test before and after temperatures.
Lucien at Innov8tive responded to my temperature question - "When I do the testing on the motor, I do not like to see the core of the motor exceed 160˚ F. That is the point where I call the “Max Current Point” on the Cobra motors during my prop tests. The “Can Temperature” will typically be about 30˚ F cooler than the core temperature." and "The magnets used in the motors are rated for 150˚ C (302˚ F) but you really never want to get them that hot. Likewise, the insulation on the winding wire is rated for the same temperature, but you can get localized heating on the inside strands of the wire, closest to the stator core, that can be significantly hotter than the core itself." "If a motor is getting that hot, then you either do not have enough cooling, or you are simply pushing the motor too hard for the application."
In 2013 when I was looking at motors, I asked about the 2826-12 vs the 3515-18. Lucien's reply - "Of the two motors you asked about, the 2626-12 actually can handle more power than the 3515-18 motor can. If you needed more power than the 2826-12 motor provides, I would suggest the Cobra 3520-14 instead. It is 1-1/2 ounces heavier, but would be able to produce more power than the 2826-12 motor does."
Looks like a "can temperature" of <130F is the goal, so more motor or more cooling, though that isn't surprising information and doesn't solve the current issue, pun intended.