We were riding the daVinci on a local century this past summer when a young college-age couple went whipping by using a home-grown version of the same. He had a sturdy-looking rack with two bungee-cords (in series) strung back to her handlebars. At the time, we were cruising at about 15 mph up a long, steady uphill; they must have been doing 20 or better. He looked to be a fast racer-boy; she definitely was not in the same league. Obviously this home-made contraption was doing the job they intended it for.
Now, for many years I've joked at various times about bringing along a bungee to hook onto various stronger rider's saddle rails to help on the uphills, but I'd never actually seen it in action.
Just about laughed my head off.
Of course, I kept wondering what would happen if she slowed down just enough to let the mass of metal where the two bungee cords were spliced dip down just enough to fall into the spokes of her front wheel.
Didn't seem like anything I wanted to be a part of, myself. On the other hand, we didn't pass any ambulances nor hear of any disastrous crashes for the duration of the ride. Perhaps they pulled it off...