I personally suspect that, for me at least, some of the hot foot that I get has to do with how tired my legs are. I had noticed that over the same distance my toes were more likely to get numb on a certain route in which I ride against the wind for the last have of the ride directly towards the beach. I experimented on this route recently after my toes started to numb. When I focused on using my muscles and having light feet rather than being lazy pressing against the pedals with my bones and feet, the numbness subsided.