Anyone tried this besides me? I tried it with a non-reporting 1.4TC on my 6D and got pretty good results, even for tracking items. When I have some time I'm going to take a picture of something useful and post the results. But I was surprised at the overall responsiveness.
What I'm curious about is whether something like the 5DIII will give single-point autofocus with this combo with a 1.4TC that fits and appropriately reports itself to the camera. I realize the camera shouldn't autofocus since it's above f/8, but since the lens tricks most cameras into autofocusing at f/6.3, I wasn't sure if it can continue the "trick" with a 1.4TC or not, and just report f/8.
Since I don't have a reporting 1.4TC that fits the Tamron, nor a 5D3,it was going to be hard to try this myself. I did searches and couldn't find anything. Sigma 150-500 owners might be able to help as well.