Lockblock for helmet use?
 

I have a Specialized Echelon that I'm currently using (it was free- won a LG time trial helmet from LBS but was allowed to exchange). I've tried mounting my cheap light that's powered by 3xAAA using rubber bands, but either I can't get the aim right or it flops around too much. And the zip tie trick didn't work for me either :(.

Also, since I'm a bike/bus commuter, I only wear the helmet while on the bike. The helmet either goes in a backpack or dangles from the top haul loop. Not sure I'd trust a lockblock to hold a light when it's flopping around on the outside of a bag like that, but maybe the mount by itself (with the light removed) would be okay?

I use a Lockblock on top of my Giro helmet with a Solarforce L2 with a single 18650 battery. Once the strap is all snugged down, it's on there nice and solid, it does't move at all.

Semper Fi

For those focused on a good helmet mount, look at the zefal doodad plus. This is normally used to mount a bike pump but works great as a helmet light mount.. The twofish bike block - it has parallel mounting is a good one too.. I found that the mount you use is different for each type of helmet, so it is best to try a couple different models and see what works best.

http://www.amazon.com/Zefal-Doodad-P...6311753&sr=1-1
http://www.amazon.com/Two-Fish-Block...6311719&sr=8-1