First time out on the blue bike with the lamp shielded. It seemed to work reasonably well with the light on normal beam, but on full beam I quickly increased my speed to 60 or 90 mph. Discounting the possibility that finally all the criding have been doing has finally had some benefit, I think I'll need to put more foil on (and test it properly this time).
Interesting that on switching down from high to normal beam, the speedometer took some time to settle down.