Hi Richard,
I find that doing the mock exam is an excellent way to gauge your readiness. From what I gathered, you still have 5 additional mock exams available to you, I'd suggest to finish them all (Bonus: Try the other mock exam providers as well). Not only do they close your knowledge gaps, they also train your exam endurance. Although thorough knowledge of the PMBOK is important, your physical condition, mental agility and stress level also play a crucial part in the actual exam.
Cheers,
Joe