I have done 6 direct trades without any type of contract. Each time the person I have traded with has givem ne a confirmation from their resort with the reservation either in my name or me listed as the guest. I have done likewise with the units I have traded that are floating weeks. With my fixed weeks, I have sent the resort notification of a guest using my unit for my week and given my guest a copy of the letter I sent as well as confirmation from the resort that they have received the information.
All of my direct trades have gone smoothly for both parties.