ga_trojan,
You have illustrated my point exactly. I was part of a couple of these operations (although for the record have not personally logged co-pilot time in anything <5700kg). Lots of PA31/C404 ops that are 2-crew operated, charter cat, under companies/ops manuals with no formal multi-crew procedures. The second pilot may do nothing more than hand fly in the cruise to give P1 a break, and radios at other times. What are they supposed to log? It cannot be argued that they're not allowed to fly the aircraft at times (assuming they're current and endorsed, of course), even if the aeroplane has no formal co-pilot rating.
It's not PIC, dual, or ICUS. So they don't log anything?