Went for a night MTB ride with my lights for the first time last night.
Setup: Fenix L2D on my helmet and an MTE P7 on my bars. Fenix attached with rubber bands and P7 attahed with 2-fish lock/bike block (I can't ever remember which is which - it's the 90 degree one).
Thoughts: The P7 overpowers the Fenix's beam even on turbo but the Fenix worked well as a helmet spot light. The P7 on the bars gave plenty of light but the mount rotated a bit on the bars when I hit big/hard bumps which was a bit annoying until I reeeaaallly tightened down the velcro. Temp was 48F and I rode for about 1hr 20min with the Fenix on Turbo and P7 on high - neither light seemed to dim.
Improvements: Having a good throw from the Fenix as a helmet light was nice but I'm curious to try a P7 on my helmet as well as the bars. Looking down long corridors of tight trees may not work as well with the wider beam though. Might cut a strip of old inner tube to wrap around my handle bar before attaching the 2-fish block next time to help with the rotation problem.
Overall: This has proven to be an excellent setup for my road commuting coupled with a Planet Bike Superflash and it works for off-road as well. A little tweaking of the bar mount and it'll be great.
Do you mount the P7 w/ 2-Fish above the bar, or hanging below? I've had better results hanging my TaskForce (C-cell) light below the bar- less prone to rotate if I hit the balance point pretty close, though it's still a bit jiggly for my preference.