No room on the bipedal sheet since that's where equipment can go.
Empty slots (including that hand/manupulator slot if the battle armor doesn't have manipulators or armored gloves) count as an operator hit, though, so only a maximally loaded (all 4 slots in the arm have equipment) assault biped armor lacks operator hits in the arms.
Also if the armor has armored gloves, getting shot in the hand of the suit also counts as the operator getting shot in the hand (ie. operator hit)