rainbowbright, check my recent posts over in the thread LEDninja linked in the second post here.
Very important piece of info that you will be on a bike, I was thinking like others here that you were looking for too much light for walking, but there is no such thing when night mountain biking. I actually prefer two of this type of light on my bars, plus a helmet mounted light. Are you racing? If you are not, and you are cutting it close on runtime for the 1x18650 lights you are considiering, you could do what I do and just carry a spare charged 18650, they are small and quick to change. I have problems with heavier lights tending to bounce on the bars, especially with the Twofish mounts. That gives me almost a strobe like effect which I hate, so I try to select a short, lightweight light, since I won't need the mass for a heatsink, the airflow from the bike takes care of that problem.
BTW, I use a simple home made mounting system for these consisting of a small block of firm foam with two perpendicular grooves sanded into it (cut from dollar store flip-flop shoes) and a silicone wrist band/bracelet (simpler, cleaner replacement for multiple rubber bands). I found an online store with plain, black bands for 50 cents a piece, shipped (bag of 20). On the road, I will sometimes add a rubber band on top of the silicone band and use it to hold a spare battery piggy-back on top of the light, sitting on the silicone band loops.