In addition to being able to request to surf with or host someone, perhaps we could offer a 3rd option:
Travel buddy Request
If someone creates a public trip they could indicate they are open (or not open) to travel buddies (and how many). If someone indicates they are open to having one or more travel buddies, then someone could send a request (just like a host or surf request) asking to become travel buddies for this trip. If they agree, they can “link” profiles for that time period as I described in this thread.