Out of interest, I haven't read everything in this thread but note a lot of people choose the Common sense approach of extrapolating data for higher temps based on the data in the POH.
A lot of newer Aircraft seem to have a Temp Limit, when you extrapolate the Data though to beyond that Temp Limit the Aircraft could still perform when doing so, but there is still this limitation.
If you extrapolate beyond the data presented, how do you know for certain that it will perform?
When designing W&B Programs in the past using Excel for various Aircraft I've often noted that a lot of Aircraft don't follow simple extrapolation, they require complicated Polynomial Equations to be able to do so, something beyond I'd say the vast majority of Pilots and unless you evaluated the entire data set you would never be aware of it, how are you certain that beyond the 40 degrees performance data stated in your POH that Performance of the Aircraft wouldn't start to significantly decrease at say 45 degrees and beyond?