Hello Andy: the only problem is the one you just pointed out: they have a magnet, but obviousy it doesn't work on our aluminium bodies.
But as long as you carry one, and can put it somewhere in the car (roll hoops, fuel cap, or any other part made out of steel, luggage rack...) that allows the light to be seen, it should be OK.
I guess you can simply put it on the bags or the back as long as it doesn't fall off. The rules say nothing about those V16 lights to be fixed (via magnet, suction cup or whatever). It says you just need to carry one and put it on the car in case of emergency.
