I've been doing yoga for several years now, and I still can't really tolerate the pressure or pain that comes with going to the tops of the feet in this pose, such that I stay on my toes instead.
For some reason, even when it DOESN'T hurt too much, the pressure causes some of my toes to cross, and it feels like they may get "stuck". It's not a good feeling.
How do you even strengthen that part of the foot? Raises? That seems to affect the ankles more than the feet. Is that where the true issue lies? (As a note, I also have weak and hyperflexible ankles, so that makes some poses and exercises challenging as well. I've been doing general strength/cardio workouts for a year and a half, so not as long as yoga, and that has rapidly helped with a lot of my yoga -- but not with this particular issue.)
Side note, but similarly my grip tends to hurt, especially when using some props to assist with yoga. I have a grip strengthener, and it seems like I almost need something equivalent for the feet, but my problem isn't with the sole...hmm...