Today I ran one of my favorite runs - Hulls Gulch - in my five fingers (5F) During the run I was thinking about how I was running today versus 1 week ago today when I was running Robie. Could I have run Robie in my 5F? Should I have run Robie in my 5F?
To answer this question, I paid for close attention to both my uphill and downhill form. On the uphill, I felt very strong. What you realize when running in 5F is that you land very lightly and you pay attention to where your feet landing - fearing the dreaded pebble you could land on at the softest most tender part of your foot. Ouch! Something you really don't need to worry about is that on your feet versus the bounding you do when you know you have soles to protect your feet.
The downhill is another question. I ran downhill at Robie at an average pace of 7:05. I know I could not have run that fast downhill in my 5F as fast as I ran in my normal running shoes. Most of my attention would have to focus on the terrain and landing instead of just focusing in on running due to the worry about pebbles and the lack of traction. And, the slush, ice and mud would have been a problem - in my normal running shoes is was a precarious situation but in 5F it would have been much worse - again because of lack of traction.
Ultimately, I'm glad I didn't run Robie in my 5F. They/me would have done well on the uphills, but the flats and downhill need some work and not enough that I think I would ever do as well in my five fingers as I did in my normal running shoes on the downhill. And, I'm not sure I would ever run Robie, or any other race that I was competing in for time, because you do have to be more cautious in your foot landing.