Sports timing using M6E Nano with a WRL-14131 antenna

Having watched the frisbee golf demonstration I am interested in putting together something using the M6E Nano with a WRL-14131 antenna for sports timing applications (primarily running and cycling).

I have a few questions regarding antenna placement. If I aim the antenna across the finish line (perpendicular to the direction that people are approaching from) how far far in front of the line can I expect it to start detecting tags? At 40kmh (11m/s) will the unit have time to identify and read the tag. The finish-line can be designed such that all competitors will pass within a couple of meters of the antenna with a clear view of the tag.

In addition to having a unit placed at the finish-line, I am considering having a unit at turn checkpoints (low speed as it is a 180 degree turn). There would be no data connection between the units. Is it feasible for the unit at the checkpoint to write a simple timestamp code to a competitors tag as they pass which can then be read at the finish-line? I realise data could be stored locally at the checkpoint and merged later but it would be good to get the data back to the finish-line asap.