If it helps, I don't think the number of diagrams has too much effect (unless you provide a huge number of it!)
I followed the assignment indications (1 class diagram, 1 component diagram, and 1 for each use case) and I passed, other people didn't followed it, and passed too
My class diagram was concise enough so I didn't felt more diagrams were required.
My component diagram was a little cluttered but I liked the "big map view" it provided.
(I lost 6 points in the component and class each, so maybe you shouldn't follow my advice

)
The sequence diagrams, some where short, so there was no point on splitting, and one was kind of big, but again, I felt that by splitting it, some context would be lost. (and I got all the points for sequence diagrams

)
Bottom line: do whatever YOU think is the best way and be ready to explain why.
[ August 23, 2007: Message edited by: Gabriel Claramunt ]