Whether convex stick-ons work depends on the specific tow vehicle and trailer.
If your mirrors do not stick out as far as the sides of the trailer, no shape of mirror will bend your line of sight around the obstructing trailer body.
If your mirrors are out far enough, but your angle of view is too narrow, convex mirrors could be a great solution.
In my case, due to the relatively wide body of my B1700 and relatively small mirrors (compared to some trucks) of my Sienna, I would need mirrors sticking out further to usefully increase my ability to see other traffic.
We discussed the legal requirements in some previous topic, but essentially the laws seem unlikely - at least to me - to ever say you need "towing mirrors": what would that mean? Instead, they set performance criteria, such as what area you need to be able to see.
1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
STATUS: No longer active in forum.