I try to pedal with my heel cups. My foot is about flat at the bottom. I think that helps to engage the hams and glutes and is easy on the feet and calves.
https://www.youtube.com/watch?v=z04uoO7U_SA
If you watch the pros, there's a lot of variation. Phinney was a toe down advocate. I saw an engineering discussion on youtube which I can't find that said the closer your shin was to your pedal axle, the more mechanically efficient the stroke.