[Yahya A.Sharif (OP)]

Placing a 15kg concrete block on one's abdomen requires one small modification for a fair comparison: the edges need to be rounded off as a sharp edge could cause inordinate pain, even with a much lighter load.

I don't think any modification is necessary, as that would create an inequivalent scenario. When lying on the block, the force is mutual: I push the block with 63.4 kgf, and the block pushes me back with the same force. This is equivalent to placing the same 15-kg concrete block on my abdomen. In other words the block applies 63.4 kgf on my abdomen, then it applies 15 kgf.

[Kryptid]

@Kryptid, can you confirm that you were unable to apply the same 71 kg weight as an inanimate mass over the same area on the abdomen?

I keep forgetting to perform the experiment.