Macro magnification math problem

So, just for kicks, I decided to see how much of a macro lens I could make. Any thoughts on the final focal length and or magnification factor are welcome.

I started with a Canon EF-s 60mm macro. Stacked on the Canon EF extension tubes 12mm and 25mm. Then, I attached the Canon EF 2x tele-extender. And finally for good measure, I put on a Sigma 1.4x teleconverter. This mass of lens modifiers is attached to a Canon 5d Mark II. In order to focus at maximum magnification, the front of the lens is just about touching the object I am shooting.

Some might ask why I did this? The answer is: because I can!

Reckon it should be near 5:1 mag. Just take a pic of the mm scale of a ruler and see how many mms you get across the frame.
Mag = sensor width/mm across frame= 36/mm across frame
Brian v.

So I thought I would post a couple of samples taken with the above mentioned lens combinantion. These are both taken with a 5d Mark II and are nor retouched or cropped. You can see a little vingetting in the corners.

HOSTED PHOTO
please log in to view hosted photos in full size.

HOSTED PHOTO
please log in to view hosted photos in full size.