I never knew anything about flashlights, "Dinottees" or "O-rings" before I started reading the gadget forums here. But as a good little grasshopper - I learned quickly.

The pics below are my "city bike" lighting setup that works well for average rides.

Straight-on shot showing big Dinottee 4-cell Li Ion battery - mounted on "space bar"


Here's another shot demonstrating old inner tube straps holding a Fenix LD20 as "O rings."


And one more pic showing strapping as well, one holds it tight, one is a "backup" safety catch.