I’ve had numerous magicshine-esque bike lights and the o-ring always does a pretty good job of staying on.
What they never seem to do (on my handlebars at least) is to shine directly in front of me, and instead shines 6ft left / right in the bushes.

What cludges / hacks do you use to get the light so it shines directly in front?

Lupine use this system;

You can adjust the angle the metal bracket attaches to the light at so it points straight ahead – might be possible to adapt for your lights?

A couple of those elastic bands the posties leave lying around everwhere to apply tactical tension to the light body

Great I’ll try both of those cheers 🙂

Bar Fly also do an “out-front” mount: http://www.barflybike.com/shop/mtb-mounts/universal/

Or something made by Minoura (although I wouldn’t recommend it for anything offroad): http://www.minoura.jp/english/accessory/lightholder/cs-500.html