Yes, you are right about the penny especially if it flutters or rotates and the air resistance. It was interesting to note that you used grams instead of the penny a 1/20th unit of weight for the troy ounce. Even though you gave the example of the pen and it is likely it would adopt a linear trajectory just like an arrow by the time it reached ground level and puncture.

The skull can accept 8 p.s.i. before damage. Try calculating what would happen if the penny hit on edge and the surface area at the point of contact with a skull. Like a record needle on an old phonograph record the needle is 20,000 psi. When one takes this amount of force into account it just might crack a skull or cause a real nasty bruise