And which category do you think that remark belongs to?

Yes, of course if the belt loosens there is a bad outcome! And MY main original point was that I don't want to rely on my homemade brackets to restrain my weight plus that of the seat.

I plan to use "old-school" manually adjustable belts as I mentioned previously. No retractors or other inertial-locking devices. One less thing to worry about loosening.