The front screen/windscreen should actually seem quite loose in it's aperture until the expander strip is fitted.

 

No pinching Jeff just a tad of frustration that the glass kept popping out of the rubber and I could not figure out why. It would go in but a couple of seconds later before I could get the expander section in my hand it would start slowly to peel back out. I thought a quite slap with the palm of my hand would put it back in place but then "Smash".

 

With the rear screen rubber as Glyn has pointed out there is a gap between the rubber and the bottom corner. The rear screen rubber is smaller than the aperture and the way to fit it is to wrap it around the screen first as a tight fit then offer the screen and rubber up to the aperture. I was once told by a Jaguar restorer that the rear chrome was a really hard fit and the way he had been taught to do it was the following.
Attach the rubber to the screen using a bonding material. Fit the expanding strip into the rubber seal. Fit and glue the chrome to the rubber seal whilst the screen is on the bench. Once all dry offer the screen up to the aperture and use the rope technique from the inside with a liberal amount of rubber sealant between the metal and the rubber seal especially in the bottom two corners..
Doing it this way he explained allowed the chrome (as long as it is the original chrome) to pull the rubber to the correct shape of the screen aperture so once it is fitted it sits correctly.
I was told this after I had fitted my screen and having broken one was not in the mood to take it back out and try his method to fit the screen and chrome all in one. Hence nearly four years before I managed to get my rear screen chrome surround fitted.



This is the rubber seal offered up to the aperture without the glass inserted showing how much smaller it is before it is stretched around the glass.

 

Just for some clarity. I'm talking about the windscreen (front) being inclined to pull away from the lower corners. Due to poor fitting & not starting by getting the lower join in the rubber centered & the lower corners correct, (pull away shown in photo above)

However when it comes to correct rubber seals the rear screen rubber seal typically appears too small for the aperture & requires stretching over the glass ~ Whereas a front (windscreen) rubber/seal should appear too large for the aperture & the windscreen somewhat loose in it's frame until the expander strip is fitted. A properly fitted front windscreen can be moved in & out quite considerably until the expander strip is fitted. No seal stretching ever required for the front windscreen. One is almost worried that the front rubber seal might pucker up somewhere it is so loose without the expander strip. If you have to stretch a front windscreen seal you will never get the lower corners correct.

I tried a number of seals because some are plain crap. IIRC, I now have COH Baines seals back & front with properly moulded corners.

Some rubbish seals actually develop a wavy pucker on the glass side of the inner corners.

We fitted the rear chrome once the rear window was in & sealed both body side & glass side & expander strip in place. Hope I don't ever have to do that again or I might try Cass suggested method.

Loctite 480 is wonderful stuff for metals & rubbers etc.

 

I look forward (a long way) to the stage when I'll be fitting front and rear screens. If I ever get that far, I will at least have good info on how to do it. Thank you for sharing your knowledge.

 

I've attached the Loctite 480 pdf. Peter. Damn expensive here but great stuff.