74,
Thanks for that link. It would make carrying the weight of an adult fairly easy, but depending on the person, and his/her disability, loading and the rigors of the ride might be problems. The more I consider it, the more sensible it seems to have the cart, in whatever form, bear the entire load without putting a significant part of it on the carrier’s legs and back — that’s for people half my age and less ;-). Just the guiding and balancing would take quite a lot of energy, in a day’s travel, let alone the propulsion.
Cry, "Treason!"