OK, you have your stand like this: ||
With the O-clamp, the light will be mounted at 9-degrees, parallel to the floor.
You can rotate the fixture via the bolt/screw/nut combination on the o-Clamp that the light actually attaches to.
Between that and the rotation that your bracket gives you, with a little trial and error, you should be able to point your light in almost any dirrection.
I mean, if you put the o-Clamp on the tube(assuming it fits the tube), you're gold. You mount the light's bracket to the clamp. Depending on how the bracket is, you may have up/down movement via tilting.
You don't have to mount the light so that the bracket is aligned to the clamp. It's nice, but it's not necessary. The fixture's bracket can be at 90-degrees off from the orientation of the flat part of the 0-Clamp where the fixture's bracket attaches.
So, you have 2 possible rotation points:
At the bracket, you can rotate through 360 degrees on that plane.
Then you have your rotation from the bracket itself. This shouldn't be a big deal unless the bracket won't let you do it.