John Gerlach wrote:
Yes, this works quite well. That is how I normally do autofocus when in my floating blind. Sometimes birds are still, and other times swimming toward me. Due to the angle I have to hold my arms in the float, it is more difficult to use back-button focus, so I keep it on the shutter, but should I get a still subject, then I force myself to press in the AF-on button to lock focus.
It has all the advantages of regular BBF in my mind, and takes care of some of the downsides, like having to hold your thumb on continuously.