Hi, do I understand it right that on a single PNR, it is the luggage allowance of the "higher" cabin that applies on all connections?

I am flying out in CE on BA, connecting to Iberia, and then returning in ET on Iberia--all one booking.

I'd like to avoid trouble with Iberia on the return leg in Economy...

Thanks!

EDIT: I am actually most concerned about hand luggage, which is just within BA limits.