Just a quick question...are you using any kind of nylon or other non-conductive material between the stars and the screws. I have been researching DIY fixtures for over a year and read hundreds of builds...almost all of the ones where screws went directly to the star resulted in shorts and a lot of re-work. You may have them there and I just don't see them.
Even these would work:
http://www.ncix.com/products/?sku=61...tech.com%20Ltd