I used an old rack's support to create a mount for my Superflash.

After using a hacksaw to cut off the extra that I wouldn't be needing, I bent the support (connects the top (front) of the rack to the seat stay) in the shape of an upside down U (with flat edges), then drilled out a couple of holes in the deck of the rack, and bolted the mount to the underside... I attached the original mount to the suport, and it works well (occasionally have to re-tighten the bolt).



Rubberside Down!
K'Tesh