This question has come up more then once during my clients training sessions.
After everybody is settled into the exercise, aligned their bodies, initiated the breath and starting the exercise. Now what to do with the feet?
Joseph H.Pilates wrote in his book: Return to Life Through Contrology, first published in 1945, that he would suggest softly pointed feet.
It is suggested that you point your feet, heels touching and stretch the top of the feet - most of my clients get foot cramps while trying to keep the feet so stongly pointed. This is also known as the Pilates stance or the V-stance.
Articulation of the foot to such extend eludes most of us. The idea of the strongly pointed foot is to activate the psoas - most fire their quadtriceps instead. The arch is lifted during this intense pointed foot. This would be a wonderful postition for some one trying to increase their arch.
For most of the Pilates exercises I suggest parallel foot position. Why?
I see too many clients already in a turn out position with miss alignment of the knees and feet, leading to all kinds of issues in the ancles, hips and lastly traveling up the spine. At times I may use a towel or a small pillow to help align the legs to reach the maximum benefits.