There is a video on Youtube about a 2010 RRS S/C - acceleration-wise the FFRR and RRS post virtually identical numbers - going from 0 to 60 in a lot less than 5.9 seconds (the speedo goes all the way to 100 and back to zero about 20 seconds into the video, but the digital readout on the TFT display helps timing the run to 60), on my watch it's closer to 5 seconds flat, give or take a couple of tenths... So your results may not be as far off the real world numbers as you think.
[youtube:1lpyly9e]http://www.youtube.com/watch?v=b-TTrrYHU-U[/youtube:1lpyly9e]
[youtube:1lpyly9e]http://www.youtube.com/watch?v=b-TTrrYHU-U[/youtube:1lpyly9e]