Handstand Push Ups on the ground may be performed with a number of variations and hand positions. However, once you increase the range of motion with deficit Handstand Push Ups, and/or decrease the base of support by using parallettes, this movement gets a lot more challenging.
In this video, Coach Carl discusses the optimal position to help you generate the maximum application of force for deficit Handstand Push Ups on parallettes. The key is finding the right width of the hand placement and get set up where your forearm remains vertical throughout the full range of motion, similar to the mechanics of a regular Push Up or Handstand Push Up on the ground. The distance away from the wall is also important so you have room to globally extend into the handstand before touching the wall to create the appropriate tension in your body for a string finish without collapsing. Don't stomp the wall with your heels at the top, kiss the wall with your toes!