Chuck you're misunderstanding what I'm doing. I haven't neglected temperature. The German protocol has included the entire model atmosphere in their calculation of IAS does as altitude changes when TAS is held constant after 2000m. It includes T and P changes and hence air density changes. All I'm reporting is that the model gives linear data that has a 1.4 percent decline per kft in IAS, quite accurate up to 40,000 ft (it changes above that).. This line gives the data in the charts that the glider manufacturers use, so I'm not messing with the safety margin, I'm simply describing it. I added a third chart to https://docs.google.com/document/d/1...it?usp=sharing to show that the 1.4% decline per kft is the right fit to the what the glider manufacturers use.

If your method is accurate, I'm guessing that if you fit a line to your results you'll get a 1.4 percent decline per kft in IAS if you hold TAS constant.