Roof rail installation ?

I was putting my roof rail gaskets in today and the F#@%$#$ thing ripped. I fastened it to the body at the rear of the door and When I held it up toward the top it liked about an inch reaching. Well it figured it was made to be stretched, so I sprayed in the glue and started working it in. Got the corner worked in, looked down and the d@*# thing ripped right about the top of the opening and ripped off one of the plastic pins. My question is..Should it be stetched that much or not? I held the other side up and it's the same way.