For a sailboat, the passenger limits seem to be limited to the number of people who can comfortably sit in and around the cockpit. For us, six is the natural number, but the boat could carry several more with no problem. The reference to cord wood is not a bad at all.
Power boats, however, have lots of interesting and often comfortable places for people to sit and participate. Unfortunately many of these are in locations that do not improve stability. We had the opportunity to observe the December lighted Boat Parade from a power boat this year. The owners were quite nice and very good hosts. Friends, family, adults, children all came aboard to join in the fun. The boat never left the dock and there was no sign of any instability, but when I thought about it in the context of the Silverton, it placed the event in a completely different light. We'll take our boat next year.
The other concern that deserves consideration is the number of folks who come aboard for drinks and snacks at the dock or in a raft up. That load can grow considerably. Additionally, sometimes we see cruise or fleet pictures with everyone who came for the fun bunched up on one boat. Maybe the dock would be a better location for the picture. Pat