The ACMS report is usually of little use in measuring G at touchdown due to previously mentioned low sampling rates (at least 16hz is required to catch peak G I believe?) and ....
G is measured in the sharp end and NOT at the gear where it should be measured - a more reliable G would be obtained from accelerometers in the main gear bay
Fuselage flexing and harmonics
Distance from G measurement to main gear?
Rotation or de-rotation rate at touchdown?
.... and I guess a few other things
A sea of O2 masks hanging out and sundry other debris seems to be pretty reliable still
