garyr_h - 12:43 am on May 21, 2013 (gmt 0)
I just received a reply from AdSense customer support about this. The rep stated that it is against the Terms of Agreement. They do not allow ANY change of the code. They even stated that the blog post that bhukkel mentioned is "out of date" and they do not allow it.
They stated that use of that code or any other code not specifically given by AdSense would result in a termination of account.