Glp,
Thanks you for your concern.
You can try this: loan a NEO from your friend for one or two minutes, lock the 'carriage' by one lock knob only (no need to lock the knob pretty tight), then put about 100 lbs weight on the top and check if the lock knob is not working or if the carriage moves. (Be creative to find the weight, or just try to shake the carriage as hard as you can).
Also try this: lock the carriage by two lock knobs (again no need to tighten the knobs pretty tight), then stand-up on the top with one leg, no matter how many pounds your weight is, then check if the carriage moves. --- Don't worry, the rest wouldn't break or damage as long as your foot is placed right on the center of the top. (Just be careful that you do not fall when trying to stand up on the top). If the rest is broken or damage I will replace it as soon as I can, and no question will be asked.
Hope this answer your concern.
seb.