Model A Pick Up rear window gasket question

Here's a question for the brain trust here on the HAMB.
I'm putting the back gl*** in my 30 model A pick up.
I'm using a new U-shaped gasket from Mac's (very good quality) but the corners kind of "pucker up"when I install it on the gl***.
Question is, do I cut the gasket a little short, pulling it together and stretching it as I put it in the frame or do I just cut it so that it covers the perimeter of the gl***? Cutting the gasket little short and pulling it tight seems to fit better but it makes the pucker worse.
I think a little heat might make the corners lay down flat but I'm not sure which way will work out better.

Any suggestions?


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Curious about this too. I have a chopped 32 cab that looks like will have the same problem.


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Cut it a little long as it will shrink a bit. Glue it with super glue. When you press it into the opening the corners should flatten up against the gl***. Cut to the top.

 

Once you put it into the opening, and install the inside trim piece, very little of the gasket will be exposed.Try a "dry run" first and check it out ( and not to sound like a smart-***,I always put the joint in the gasket at the top center of the gl***)

 

Thanks guys! I was going to cut the gasket short. That would have been a mistake.