I wanted to get a couple minutes with the Canon 100-400mm from LensRentals.com to make sure it worked with my camera.  As coincidence has it, mama Fox appeared in the lawn and sat down for a rest.  I grabbed the camera with the 100-400 on it and fired off a few images.  When I was satisfied, I attached the 2x Teleconverter just to see if I could do it.

The 2X Teleconverter takes away two stops of light.  The sun was going and I was losing light quickly, so I had to crank up the ISO to be able to hand-hold it.  The teleconverter also disables autofocus, so I had to rely on manual focusing!