"This new mount puts the original Ixon Speed, Ixon IQ Speed, Big Bang, Ixon IQ or Ixon right above the front tire at the fork crown. It's all nylon, so it won't break from fatigue like metal mounts can. If you have disc brakes, or V brakes, or old style cantilever brakes with a true wide profile, like the Paul Neo Retro cantilevers, you can use this bracket. You can't use it with low profile cantilevers like the Paul Touring, and you can't use it with any sidepull caliper brakes. The light mounts to the front of the bracket which has a cylindrical shape, just like a handlebar. 6mm bolts to attach it to the fork crown available here. The crown needs a 6mm or 1/4" hole. The mount is 3/4" thick."
I have v-brakes and a water bottle cage that will probably never be used for anything that I have to drink, so that would be a good place to stash a battery pack. And my handlebars prevent proper aiming of any 'to see by' light .