After I posted this, I took the old
radiator to the dealer and we compared it with other diesels on the lot. There was only one and that had the 16mm core. The
radiator I have put in is an aftermarket jobbie and the manufacturer may have taken it upon him/herself to step the diesel one up to a 26mm core. Maybe this is the heavy duty one 5th is talking about. The standard one is bloody skinny and the dealer was all too quick to blame the bullbar for blocking airflow.
He did seem surprised though that cooling would be overly affected by the bending of approx 20% of the fins.