We fly two crew corporate on various types. On JAR types there is no distinction between P1 and SIC as far as licencing is concerned. If a type rated crew member is driving (his or her turn, which in our outfit is most of the time) we let him or her log the time as P1. Simple really, - old farts in LHS don't need to log time, so why not give it away.
On types that a crew member is rated SIC only, (N or validated on other registrations), whatever role he or she flies, it is logged as P2 - only because they are not licenced to fly as P1, so it would be muppetry to try and claim it as such.
Deefer dog.