not sure if this is the right forum...

a friend of mine is soon going from ZRH to OSL. The M ticket is LX, but the flight SK, and he is wondering about Ski equipement. LX has 20kg, SAS now 23kg limit.
Seems both airlines do not charge for winter sport baggage as long it's within the weight limit, but each is stating this is for own flights only. So we're confused which rules would apply, LX or SK?
He doesn't have any status or even FFP. Can we link one of my *G (LH or SK) numbers to the booking, if we're on the same flight (separate bookings, and my own baggage would be on the limit..) ?