Apologize. Hectic work schedule and sleep less ( or less sleep ) days are the reasons for the delay, typical of people like me engaged with startups.
Part IV is half finished and I have to draw and scan some inscriptions and write about them. I shall post it to the group before Monday. Whole of next week I'm in Taiwan ( any PS group member living in Taiwan please send contact details and we could meet Tuesday / Wednesday evening ) and I will post Part V a week later.