How do I get an inmovable physic object to rotate properly?

I'm trying to get an object to rotate from a point while also being a physic inmovable object (because I want it to interact with other physic objects while rotating). The problem is that when an inmovable physic object rotates (wether by changing the angle, with the rotate behaviour or anything similar) it takes the centre of the sprite as the rotation point, instead of whatever centre point I have defined. Here's a little demonstration of this:

https://dl.dropboxusercontent.com/u/115 ... 0Test.capx

The blue bar is just a sprite with the center on (0,15) and the rotating behaviour. The red bar is the same sprite with a different colour, physics behaviour (with inmovable on so it has infinite mass) and the same rotating behaviour. Is there a way to make the red bar rotate in the same way as the blue one, while keeping the inmovable thing?

Create an invisible rotating sprite, position it to the point you want the red bar to rotate about and then pin the red bar to it.

It seems to work. Thanks a lot for the help.