I feel your pain. Last summer, we arrived at our vacation destination to find that my front fender had beaten itself to death (torn through). A better strapping job would have prevented it. Since these fenders (mud guards) only come in sets, I now have an extra rear one in the garage. Rear mounted auto racks (whether hitch-mounted or strap on) place some fairly delicate equipment at right angles to hurricane force winds for hours at the time. It's actually amazing that our bikes survive as well as they do, but we certainly need to carefully out think the whole process before and check often during each trip.
CC