I just received my 500 PF and picked up a really good deal on a barely used D500 to try out Nikon specifically as a dedicated combo for BIF, possibly moving up to a D850 in the future if I like the system. I own a fair amount of Canon equipment including a 1DxII, 5DIV, 5DsR, 400 DO IS II, 1.4xIII 2xIII and various other lenses mainly for landscape, dance, events, etc so at this point I am just testing the waters with Nikon to improve my falcon photography.

I will mainly be using the 500 PF for peregrine falcons in flight so using it bare to maximize speed and accuracy most of the time. However, there will be times when I expect to need to extend my reach with slower distant subjects including perched birds, mammals, slower BIF etc. I don't expect any TC combo to maintain adequate speed for an erratic bird moving in excess of 200 mph.

So, I am curious if anybody has used the 500 PF with both the 14 TC II and III and noticed a justifiable improvement on the III. Or can I accomplish my task with the II version? I've seen mixed reviews on line and its depended on the lenses in question. Since the 500 PF is so new, I'm not finding any information on the combination.

Thank you!