Supposedly MKX considered an F4 rating for the Stoughton, WI tornado of August 18, 2005 (which just missed the house where I was living at the time/where my parents still live). They settled on high-end F3 which seemed to be the standard of '05-'06. In my amateur opinion, that was an accurate rating though. The well-built houses in the worst damaged areas generally had textbook F3 damage (only some first-floor interior walls left standing). Houses that were swept away were poorly anchored "sliders." Vehicles were moved/flipped but not hurled long distances and mangled beyond recognition.Well there was one tornado in 2005 that was rated F4 and two were rated F4 in 2006. I believe they were Madisonville, KY, Monroe City, MO, and Crosstown, MO. That Westminister, TX in above photos was definitely stronger then the three I mentioned. There was also a couple other tornadoes in April of 2006 that should have been rated F4 as well. MEG did those surveys.