J, firstly welcome to this forum as it's great to finally see more Sydney owners. It seems Classico with his GranTourismo has been one of the very few.
I'm also a member of Club Maserati, so if you're interested in Sydney centric gatherings and runs you can google the website, or pm for details.
The next run is to the Blue Mountains in July.
Back to your topic. The upholsterer I use in Canberra had a GranSport in recently with a shrunk leather roof lining due to heat. He had to remove it and replace front and rear sections.
I'm sure Shaun could fix yours, it would just take a drive to Mitchell ( northern suburb of Canberra ) as you know about 3 hours each way.
Again pm me for details, but at least he has recent knowledge of the task, and when I saw it the lining was out and the seats were untouched.
Regards,
Bruce