I dont want to jack the thread so much, but I do have the option to get these made in steel, would be DOM, and would be very similar to the sparco style bar...
But would need a decent list of interest to get the ball rolling...
I have made one for our m42...
Hinged is generally a bad idea as it allows the energy to transfer through the hinge as opposed to being solid...
The rubber bumper on the valve cover seems like a really bad idea, as its more of a fix for another problem (weak engine mounts)
And aluminum would have to be square as mentioned HOWEVER aluminum doesnt have the ability to flex several times like steel does, so as the loads transfer into the bar over and over, you will eventually weaken the bar, whereas steel has spring to it. Bend some aluminum tube, and bend some steel tube, you'll see the difference...