That not quite accurate. Gorillas are much stronger than humans proportional to their mass - but become fatigued much more quickly. A human can chase down a gazelle, which is mostly muscle, and the gazelle will die of exhaustion. There's a power to endurance tradoff in how muscles work, and other features related to bodymass (such as heat elimination) which play a large role as well.
None of this should discourage you from fiddling with the encumberance scores for bandar or for giants, but don't pretend that it makes any physical sense, because it doesn't
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