Hi Grant
There is a model of the Harriet Mcgregor in the Tasmanian Maritime museum in Hobart. not sure if they would send you photos, but worth a try.
there are a lot of photos at the tas state library, that may be good for reference, they are accessible on line.
another place for information is
https://trove.nla.gov.au/newspaper/result?l-title=10&q=%22HARRIET+McGREGOR%22
I have been researching the mcgregors ships for a lot years now and still have a long way to go, I am planning to build the Harriet model myself.
i am very impressed with your model I would love to see when its finished.
Regards
Andrew