Yamaha pw haibike derestrict speedsensor

I have a Yamaha pw ebike and i have read about the derestrict modification you can do by just repositoning the speedsensor and magnet from the wheel to the pedal. But my question is if anyone have tryed to just add one more magnet on the opposit side of the original spokemagnet?

Sorry about the bad eng. Its not my native language.

Best regards P A
Doing that would make the computer think that the wheel is spinning twice as fast as it really is, thus effectively reducing your top speed, no?