Most light aircraft are unable to produce longitudinal accelerations sufficient to cause a dangerous effect
Agree. But over the years I have read accident reports where the Light aircraft have crashed during the initial climb after dark night takeoffs. Because of lack of FDR's in light piston singles and the pilot was inexperienced, it is anyone's guess what caused the aircraft to crash. Mostly it boils down to poor instrument flying skills in IMC rather the pilot being affected by somatogravic illusions.