Funny, they used the same GPS unit from Garmin WE used to use to measure top speed.
Now we switched to the Magellan Roadmate 700.

The 10.7 accel. time from 0-125 mph for the SLR and Carrera GT are highly disappointing. The GT2 Mk2 does 0-125 mph in 11.7-12.1 seconds (three different tests). Even the 10.3 sec time of the Enzo disappoints a little bit.
But nethertheless...impressive beasts, I would love to own them ALL.