I have been thinking a bit about the safety rules for multihulls as they relate to the safety rules for mono hulls.
As a conceptual matter, it seems to me that one should approach safety rules in a probabilistic way—i.e. focus rules on the most likely events. If the likely risks for Multis and Monos are different, the rules should be different.
In practice, however, when we adapt the mono rules for use by multis, we tend to simply add multi specific rules—and to never delete rules that address dangers which are less likely for a Multi.
For instance, one might add a rule relating to unsinkability or nets for multis—but we never think to remove or loosen rules that relate to the swamping or down flooding, which is less likely on a multi.
Or take personal MOB equipment. It seems to me that the dangers for multis and monos are a bit different. The more likely danger in a Mono is falling off a narrow rolling work platform. The risk on a Multi is more that getting trapped under the nets in a capsize. Thus for a multi, it might be safer to have a drysuit and a kayaking vest than a tether and a 33 pound inflatable PFD. In fact the tether and the 33 lb pfd might be more hazard than benefit. But I suspect that there would be quite a bit of resistance to changing the tether and PFD rules.
Curious to hear from anyone who has worked on these issues.