Question about windshield install

[saxart]

I'm going to be installing a windshield in my '70 this weekend and was wondering if it is possible to install the windshield, then later sneak some urethane between the gasket and the pinch weld if it had some leaks once the install is done? (I hear they like to leak near the upper corners)

I've never installed a windshield before, so I'm thinking it would be nice if I wasn't dealing with urethane all over everything while trying to finish the install. For what it's worth, I'll be using a brand new 'Precision' brand windshield gasket for the install.