Dag,
Observation from a fan who watches a bit of F3a.. As you know, the box is 60 degrees either side of centerline with the airplane 150m out. I have timed a couple of top pilots flying this line and it is an 8 count. In the vertical they do a four count. one one thousand... two one thousand..... ... ... So with a length of the box at 519m that would be 64m/s or 143 mph. of course if that was a 9 count = 57 m/s or 127 mph or if it was a 10 count = 51 m/s or 114 mph
Ken
PS: tae the math for what it's worth.. based on observations,, not radar..