I had just one component diagram.Dont worry abt the number of components I had.I showed all the major
EJB's,Controllers,Facades,DAO's in the application and it looked pretty decent
Infact i was not sure whether i can score good marks with it but i explained all the components/patterns in my small assumption document.As long as you can explain your design,yours will be the best.SUN doesnt expect a perfect design(infact its difficult to have one too) but a design which you can defend and show that it fulfills the requirements.
Good luck with ur preparations