[Low-Tech] Boating vs Shiphandling

[Dalillama]

What is the cutoff between the Boating (Sailboat) and Shiphandling skills? In Low-Tech, vessels up to the size of the 50' brig are listed as using Boating (Sailboat), but in LTC 3 the 30' dhow and fishing junk are both listed as using Shiphandling. I had supposed that Boating pretty much only applied to vessels that one could at least theoretically singlehand, and Shiphandling/Crewman was needed for vessels that need a multi-person crew, but this appears to not be the case, since there's no way that one person can run a 50' brig, for instance.