This first shot is with the 500 II and 1.4 T.C. II mounted on a Monfroto video tripod, and a wimberley II head.
First, I do not like locking the head down. I snug up the tension with the horizontal and vertical adj. knobs only. That way I can easily re-compose if needed.
Next I set the IS to 3. That lets the IS engage only when the shutter is pressed. I like this mode much better when shooting on a tripod at low shutter speeds. As opposed to BIF when I set it to mode 1. IMO, better than mode 2 when doing BIF? Just me I guess.
Shot at 1/50, ISO 1250, F/5.6
Next I turned the IS off. I didn't like any of the results with IS off using the 1.4 T.C. But! After I took off the T.C. I had no problem at all with IS off. Beautiful, sharp shots. With minimum effort.
This is with the 500 II without a T.C. 1/100, F5.6, ISO 1250.
When you shoot with the same camera and lens as much as I do. It becomes second nature to me. I don't even think about it anymore honestly. I check the settings instinctively and know where the exposure basically needs to be set, adj. AF points, before I ever take the shot. Maybe one second max.
These little tests help me! It helps me in being more confident and decisive. I take action and implement the changes with confidence as the conditions change. Everyone shoots differently. Everyone need to know the limits of there ability. With the gear they use. Some use the 2.0 x with no problems. Some hand hold with T.C.'s.
It is endless!
Get out and enjoy it. You don't live forever.