lol! I do have flip-flops, three pairs at least. I always bring back a pair from Thailand, the generic blue and white ones (elephant in a star brand) are my absolute favourites.
Love the idea about turning them into fender mud flaps!!!
Strapping them under the rack is a great idea!
edit: nope, not enough clearance between rack and fender. Quite thick rubber soles on these, they actually weigh 400g, yikes!! that's 14 oz!
Maybe I should confer with the ultralight gang!