Installing Windshield Stainless Steel trim?

We will also have to install the rear window stainless steel trim. That glass also has a new gasket.
Compounding everything is that the car also has had a new vinyl roof installed and the two seams in the vinyl material are quite thick where they meet the window channel.
I was just wondering if it make any difference to start attaching in the middle of a piece and work out to the ends or to start at one end of a piece and work across to the other end.