You have to understand these sensors. People say they react to metal interfering with a low frequency electromagnetic field, and you need to find the sweet spot, put the heaviest metalic spot on your bike over the sweet spot of the sensor, etc.

They're all wrong.

These things are actually set up to sense a bicyclist put his foot down. If you can do a track stand for 3, 17, or 70x7 seconds, and then put your foot down, the light's going to change two seconds later. It's a conspiracy to make you clip out!