I now see the problem. With the top down you can better see the strip of rubber that meets the top edge of the upper windshield frame. That rubber is tight to the frame all the way across except for an 8 inch stretch in the middle. Hard to even see, but tape on that section stopped the whistle. I'm trying to see if that rubber is held with adhesive. I don't see a channel to push it into and it does not look torn or damaged. I don't see this strip mentioned in the service manual either. I may try a thin line of adhesive.