I watched the crash repairs mob do mine the other day.
They attached the seal to window all the way around.
I mentioned to them , that i had read a post on here where a blokes 18 month old windscreen had started leaking !
They put some sort of windscreen sealer in the top fold of the windscreen seal.
they put some 8mm heavy braided cord in the grove that goes on the flange of the body. starting on the bottom, 6inched to the right of centre alll the way around , clockwise, until the cord was back to the bottom overlapping where it had started by 200mm.
Three people lifted the screen up into position and centered it. With one person applying pressure where the overlapp of the cord was at the bottom of the screen, a person inside started pulling the cord out slowly, at ninety degrees to the edge of the screen.
As he was doing that the screen/rubber seated down onto the "body flange", seemed to take a bit of extra care at the corners. When the cord was all out the job was done , with just a little tapping with the palm of the hand to bed it down a little .
Now if mine leaks on 18 months I can take it back!
Don't know if the above helps,
cheers Greg