I had the shimmy on mine to start with as well. It turns out that the
front wheels had loose spokes. It did "bad things" I happened to be
in Florida and ended up going to big cat. They went over both front
wheels.

This fixed most of my problem, but I found that on strong down hills
that I still had a small amount of shimmy. When I rode tour Dallas
and hit a big bump I felt the head set in and no longer had any
problems at all. Since then I took my bike back to Mark @ PowerOn for
a checkup and everything is perfect.