Thanks for such prompt and helpful replies!

Brant, thanks for the advice and the link. I had actually found that video, but wondered whether his numbers were representative of what others find. It seems a very helpful video overall.

Joel, you make a great point. Very low shutter speeds are not likely to be useful for any real subject (rather than the label on an appliance I used as a test target). We should all think more in terms of the lower ISO that could be achieved. Shutter speed is really a convenient stand-in for lower ISO for these comparisons.

Both HDNitehawk and Joel make the important point about how much the weight of the lens could matter. I am using the Canon 400mm f/5.6 and the 5DIV so total weight is not such an issue. I suppose that is the reason I can use a ball head at all. However I might sometimes rent a heavier lens. Then the ability to manage the weight better on the gimbal could be very important. And it certainly makes sense that if there is no strain on the hands to support weight in any direction that it would be easier to avoid shake with even a lighter lens.

And HDNitehawk, very useful link. I did not really understand the vertical adjustment well until I saw this video.

If I decide to buy a gimbal, I will be sure to post a follow-up here.

Thanks again!

Danny