One thing to keep in mind about helmet-mounted lights: a lot of engineering goes into helmet design to reduce rotational force in a crash -- this is what MIPS is all about, for example. Hanging something off your helmet will increase the chance of your helmet getting hung up on the ground while your head and body keep moving - which is a bad thing. Perhaps the additional safety provided by a helmet light is a reasonable trade-off for some riders, but it is something to consider.