Hi, this is my own attempt on a shoulder support. Tested it: works well. Especialy with the heavy battery at the back (it is for the oncamera light - can be removed in 5 seconds :) )
Here is the support finished with XM2 mounted:
http://w1.226.telia.com/~u22607422/CanonOnSupportSmall.jpg

Here is a detail (before painting):
http://w1.226.telia.com/~u22607422/support3.JPG

Wow. Well done... Is it made of aluminum?

The curved plate that goes on the shoulder is alu, indeed. The rods are PVC. But strong PVC, at about 5mm thick wals... It was just what I had in the house... I kind of made up my mind in a minute: "hey, I have three hours to spare, what should I do?! Got it: a shoulder support. Let's see what materials do I have..."
Something like that! :)