That looks like the trials hoop. There are some pics near the end that are just the hoop with the fender removed. If you want it more minimal I wonder if you could even remove the top hoop and just have the loop that goes around the outside. This was designed to hold an alloy fender which is more flexy than a steel one.
It looks like it bolts to the shock mount and the subframe mount just forward of that, incorporating mounts for the seat springs along the way. If nothing else, a piece of flat bar mounted like that could make a nice place to mount a custom strut that follows the fender line. Then you can just weld to the strut and bolt to the frame. Easier than having to weld right to the frame.
Or make it really slick, run some brackets inside the fender. Lots of cruiser have internal bracing for the fender.
Only the first option is bolt on but you could get the bracket and chromed it would look way better than what you have now.
Scott