By mounting bolts do you mean where they bolt to the frame as in the second photo? From what I’ve read the real death trap is the bolts inside the fenders that secure the two side straps that gets caught during a bump or vibration like in the first photo.I will sometimes cut small squares of old inner tube & poke a hole in middle to use as rubber washers on both sides of fender mounting bolts - leaving fender just a bit loose on these will often be enough, but keep a good eye on them for a while
when this doesn't seem to be working, I'll cut some heavier steel and replace the thin hangers for the fenders (still left just a bit loose)
Okay I can reinforce that but I thought most people were having issues with either the front or back fender catching towards the rear of the tires and then burrito-ing up into the frame? And does leaving them a bit loose keep the vibration down or something? Leaving anything on this bike a bit loose makes me nervous ha.2nd photo - that keeps fender from dropping onto tire
that thin tab there will rip right across due to vibration - I use an extra gas tank mounting strap cut in half if I want it tight