Yes, I've don it with a number of lenses. The 1.4X goes next to the camera, and the camera only sees the 1.4X. I could mount it to my f/4 lenses and get autofocus at f/11 that way. AF at f/11 is hit and miss.
Here are a couple I took recently with both TC's, my MK III, and 70-200mm MK II. The aperture was wide open. This was before the f/8 firmware update, it wasn't needed when you stack TC's.