Here's my method which has worked well, but I warn you it's not the prettiest. On a dark/smoked windscreen it's alright, but I probably wouldn't do it on a clear one.
With everything nicely held in place, melt/cut a trough in the back of the windshield with a soldering gun (I got my 230W one years ago from radioshack f
or about $30, but 100W or probably a lot less would work just as well) so everything is attached correctly. Scrape up the burrs or lightly sand with rough grit, and then fill in the trough you melted with plastic epoxy
Super cheap to do, and works just fine.