Try using power pads if you haven't already. My feet would cramp up within a couple of miles and I tried everything. Thick soles, thin soles, relaxing while riding, carving more, shifting my weight around, wiggling my toes, positioning my feet further forward on the pedals, getting larger pedals, frequent stretching, and simply riding more. But after 200 miles and no improvement, I asked this same question and my buddy recommended power pads and they eliminated all cramping for me!! Being able to accelerate with forward motion using your shins relieves your feet from having to accelerate by applying downward pressure.