I would suggest that you place the shadow on Zone III and increase development by two stops thus giving yourself 4 stops of contrast where the brightest highlight will fall on Zone VII. You could also increase the contrast by using a harder paper grade. To increase development by 1 stop increase the normal development time by 25% and add the two times together before calculating 25% of the answer to arrive at the second stop increase.
For example if your normal dev time is 10 mins, divide by 4 = 2.5 mins therefore 1 stop increase = 12.5 mins divide by 4 = 3 mins therefore 2 stops increase =15.5 mins. Ignore the few seconds difference in the second stop calculation.