that link was pretty awesome.
i have always recommended when you are using belts, use them only above 80-90% for lifts heavily using the spine. where exactly depends on the lift and the lifter.
i have been pushing without a belt until this week. i have been squatting 150% of my BW and DL 175%. i do lift with experienced powerlifters/strongman competitors and we do film each other on heavy days so check form. i would not recommend pushing that much without a belt for most people.