Good advice above from FB and others and some from others mistaken. As an ME with years as a design engineer I can tell you nothing anywhere is that simple. Marketing puts pressure on designers as trying to make something safe that any mortal might try will make the product too expensive so the pressure is to strike a balance with what reasonable people would do. Safety margins get very complicated as you must consider material stress reliability with component reliability. As an example in aerospace we used safety factors of 1.4 for ultimate strength, and 1.25 for yield based on NASA STD 7001. If you tool around your block under 10 MPH maybe no worries, in an unpleasant situation your a big man and could put a nasty load on that steerer and I bet you find other things that are not designed for a man your size.