Someone on rllmuk tipped me off that Extra Mode 2 was the best one to try for the Crown, and lo, he was right. On my first go I got loads of them! Managed a score of 381,000-ish too, so I was prompted to keep trying for a 400,000 score, but every further attempt just got me less and less. With my final go I just scraped 92,000. Weak.