I ended up redrilling and tapping the screw holes for the back window. I had used 6-32 screws and they just didn't seem to fit tight. So, I redrilled and tapped for 8-32. But, when I went to put the window on, a few of the holes were out of line. I drilled the hole a bit bigger in the direction it needed to go and re-countersunk the holes. It seems to work better now.
