I forgot in my post above, the best solution:

On my rack mounts, I use long enough bolts to stick out the other side. I started this because a bolt sheared off (the LONG one below, probably because it loosened first, so then big bending load) and I could just barely back it out with a dental pic; With bolt sticking out the other side, it's easy to extract. BUT ALSO, I then put a plain nut (stainless steel, like the bolt) on the far side, slight torque, and if bolts were to ever loosen before, then won't now. Further, I use anti-seize on the threads, and, once torqued, put a dot of red nail polish on the 12 o'clock (top) position of the bolt head, so I can see at a glance if the bolt is coming loose. And I carry spare bolts. This is my recommendation for loaded touring bikes, better than loctite, because there won't be a soldering iron in the field to soften the locktite, though a torch lighter would probably work. An assortment of long rack bolts, M5 sockethead stainless, 5 lengths with 5 or 10 each length (can't remember), was like 7 or 8 dollars on amazon.