I had a three corner tear in my TR6 top 8 years ago.
Repaired it and it still looks as good as the day I did it.
I used a product called VIP. It is a contact cement used by professionals, I asked one and that is how I found out about it.
Then I found some material that was close in color. Went to an upholstery shop and they gave it to me.
Then I followed the directions and applied the glue to the underside of the top and the patch. Then placed a small board under it and one over it with some weight on to hold things in place while it set up. Last was after it had set I applied a small amount to make it look nicer on the outside.
The photos are as it is nearly 8 years and more than 30,000 miles later.