Since the base can not grip with the feet, balancing the flyer by using the shear forces is not possible. The base must always remain under the center of gravity of the flyer. In the position “headfirst” the base also has no line of sight to the flyer. This actually destroys almost all possibilities of balancing through the base. Either the flyer is so experienced that it remains in the line of force without causing any shear forces, or another base takes over the balancing…
Standing on the head or shoulder, the line of power is distributed on 3 contact points. However, the line of force is not vertical, as also the spine of the base is not perpendicular in space.
This form of balance is not suitable even for advanced and usually only useful with multiple bases, because then the balance is ensured by the lower base.
Balancing in the handstand is like sitting on a 2-legged stool. A tilting of the base usually results in a tilting of the flyer! Any base who manages a trick in this position should register quickly at a circus contest (like Monaco)!