Almost every magazine article that I ever read about the Crossfire, mentioned how "stiff" and "vault like" it's construction was. That it had the "solid" feel that was usually associated with cars built by M/B, the coupes especially.
I'm with PATPUR on this one. Where do these people come up with these "helpful suggestions" about this car?
You should encounter no problems jacking an XF up, using the designated "jacking" points as shown in the owners manual, doors opened, or closed.