My wife's bike has no room on the seat post, and a rack with no bracket or holes drilled to mount a light, and she often uses panniers so seat stay mounts don't work. So I came up with this DIY idea. I clipped the light on, drilled a 1/8" hole through the plastic clip and rack, enlarged the rack hole to 3/16", then drove a sheet metal screw, tight in the clip and loose in the hole. Feels good and solid.
