However sophisticated, however comfortable it may be, harness hanging is not physiological.
Accordingly, as being evidenced by the investigations mentioned as a note, a person being accidentally hanging in his/her harness should be "de-suspended" as soon as possible.

It takes from 6 to 20 minutes of inert suspension for a good health subject to loose consciousness.
Such a loose of consciousness leads to death without a rapid intervention.

Hanging point being ventral, sternal, or dorsal does not matter. One of the investigations concludes it is illusory designing a harness avoiding such a problem.

1) Here, we talk about inert suspension. However, problems evidenced during inert suspension arise from causes also existing during a "normal" hanging. Especially blood circulation troubles into unused legs.
That's the reason why working being hanging in a harness should be proscribed since its duration exceeds 30 min, (especially since such work is static). Using a suspension seat in conjunction with a fall-arrest or work positionning harness is essential after such time duration.

2) If there remains unavoidably a risk of hanging as a result of any fall or strain, for carrying out some works, we might be lead to contemplate, as well as implement, a fast unhooking system, as a preventive measure. Particularly as the yard is remote from any professional first-aid post (firemen, hazardous environment intervention teams, climbing dedicated rescue team, etc...)