Your research is correct, it is very hard to predict response time in a given application without doing in situ testing. As they say, the proof of the pudding is in the tasting.
That said, Tom Kerlin's book on Industrial Temperature Measurement does the best job of accomplishing what you are...
New to this forum and chiming in a bit late.
On extension wire: To optimize accuracy, request actual thermocouple wire rather than "extension grade" thermocouple wire which has worse limits of error than standard grade or special grade thermocouple wire. Your distance should be no problem so...
Since this post was first made the ASME PTC 19.3 TW (2010) standard has been published and significantly changed the standard means of assessing wake frequency / vibration issues.
As a thermowell and sensor manufacturer hoping that we could help users like you, we built a free software...