jefnvk, A threaded eyelet could be better if you wanted to use a lock nut in conjunction. Otherwise, tight is tight. If I had only one eyelet for both fenders and a rack, I'd place the rack's vertical stay next to the eyelet with the fender stay outboard of that, or place the fender stay inside of the eyelet.

If I had a rack that was swaying / flexing, I'd look at the rack's horizontal stays. There maybe a better way to secure the rack? While I doubt it, don't rule out the possibility of frame flex.

Brad