Correct way is to fit the corners first allowing seal to droop between each corner
Push seal into the corners so it is not stretched
Then fit the middle of each droop leaving smaller droops repeat fit the middle of each droop and so on
Warming the seal helps
The top corners are a BAD design the seal barely touches ?.....some designer at Porsche did not know how to cut compound radial sections

............( I was a Car body in white engineer in a previous life) spend many years designing glazing and body seals
