Hi AceCo55, thanks for the very interesting comments on this thread too!
I DID have all the room I needed to use a wider aperture, the faster the shutter better. Interesting learning from these two threads: one setting only does not fit both full bodies and close ups. I should use wide apertures for full bodies (where the AF is more "relaxed" and you need to isolate the subject) and narrow ones for close-ups (where the AF is heavily stressed and DOF is low anyway). This is an interesting thought that I can't wait to experiment and that wouldn't have crossed my mind without the conversation with you. Thanks!
Number 2 is the only photo in the set that has been significantly cropped! Interesting that it is your favorite. By the way, they were the first 2: the winner, an Ethiopian, and the runner-up, an Italian.
Number 4 is the only one in the "second" of the two angles I tried. One of the official photographers of the race was shooting right next to me and I thought that meant the second angle was better than the first one! I actually thought that the reason for this was exactly the light coming from a side, which makes shapes more three-dimensional. I probably made some mistakes in post-production.
Thanks a lot again for the good words and for the very useful feedback!