Does the dash have to be in to install windshield

I reversed the dash mounting hardware when I had my 67 fish apart. I found the threaded neck of the 'U' nut the same height as the nuts head and the screw length didn't really need shortened although I did go ahead and trim one thread off of each at grinder. Still to this day I'm not sure why I did this. I guess only because I could. I'll never remove the dash again.