>a big gap between the shoulder and hand where the blasted stone will need to support itself And there are various examples in nature of stone arches with a sp

>a big gap between the shoulder and hand where the blasted stone will need to support itself And there are various examples in nature of stone arches with a span supported on two sides. It's not as though stone is incapable of spans, it is the geometry of a span. This is a straight span, not an arch, so the distance that can be spanned is maybe shorter than an arch with similar proportions. And bear in mind this is granite, not sandstone, which has twice the compression strength and tensile strength. The thickness of the granite arm, relative to the span, is a factor. Also the integrity of the granite in the arm after blasting. Also the supporting elements, are they able to be pushed apart (an important failure mode) - seems unlikely here. >Mount Rushmore was also never completed. The design also included the presidents upper torsos. That is very interesting! And a good point, they limited scope.