Hi Dylan,
Welcome to the junk rig community. I agree with David and Paul that the sail set up needs examining based on what is today's best practice. When Michael bought Shantung back in 1978 with the junk rig in place he mentions in his book that there was nobody to ask about how the junk rig works. Fortunately this is not the case today.
Shantung is part of New Zealand maritme history being the first (only?) junk rigged vessel to have sailed around the world with a New Zealand flag. I was fortunate to hear Michael give a talk about his voyage to the Auckland Islands on Shantung - at 50 degrees south this was not an easy voyage. It was however, good preparation for his circumnavigation.
I do hope you have time, Dylan, to join the New Zealand junkies at a junket sometime soon - maybe at Kawau Island around Labour weekend?
Rob