I have HighTechSystem'sMWHS

I do like the table. Lots of holes and well-ground surfaces. The side plates with the 3 oval holes are good.

So I've got 1/4" metal work here and trying to use the eccentric cam pieces. That's the bushings (as shown in the link) which are perfectly round and screws with the sides of the head ground round but eccentric so as you turn it, the bushing wobbles in circles and at some point is supposed to press against the side of the work. The eccentric-ground screwhead fits snugly inside the cam so the cam moves with the head.

Now that I'm trying to use them, I'm not really sure how they're supposed to work. Is there supposed to be clamping from the top at all? (there's no top clamps in the kit) When I try to tighten up against the work by turning, I get this:
The bushing will always be above the table, since if you tightened it against the table it won't be at the exact angle needed to press sideways against the stock.
With the bushing not tightened flat against the table, when you tighten it by sideways pressure against the stock, the bushing wants to tilt slightly and it makes the stock float upwards off the table. Just by a few mils, being held securely just not against the table. I couldn't find a way around it really. I guess if I had an exact shim under the opposite side of each bushing to keep it from tilting, but it doesn't seem practical to pull this off.

It's 1/4" bronze stock and only a couple of inches wide. I doubt the side compression is causing the stock to flex. It's just the cams leaning and popping it up.

Am I doing it wrong? How is this supposed to work?